Polar Bears Dice Activity in AP Computer Science

A few of years ago, computers weren’t ready for AP Computer Science the first day of school. So, on the first day of class, I resurrected an opening-day activity I had used in Physics: the Polar Bears around an Ice Hold Puzzle. There are a lot of similarity between my physics and computer science classes; so, I thought the activity would be a good fit.


I was surprised that not only was the activity a good fit, it was more successful in the context of computer science than it was in physics. I’ve done it every year since, even as the computers are working on the first day.

Our discussion after everyone solved the puzzle focused on how this activity was an analogy for how our class will solve computer science challenges throughout the year:

  • You may feel frustrated as you try to figure computer science concepts and challenges out. That’s okay.
  • Computer science concepts and challenges are hard to understand until you know the “rules of the game.”
  • But, once you discover the rules, computer science concepts and challenges often seems easy and you may be surprised that others don’t understand.
  • However, remember that you didn’t always understand.
  • When you discover the rules and understand without someone just telling you the “answer”, you are excited.
  • The journey to understanding is very important. So, no one is going to tell you the answer, but we’re all here to support each other on our journeys.
  • Being told the “answer” at most gives you one answer that you didn’t know.
  • Learning to think critically and arrive at the answer with support develops a skill that you will use to find many answers.
  • Students who solve the challenge should offer suggestions as to how to reframe the game that helped others solve the problem without directly telling them the answer.

The reason that this activity worked even better in the context of computer science is that it also serves as an excellent example of best practices for algorithm design and debugging. As we continued to try and solve the puzzle, students introduced several important ideas:

  • if you just keep guessing, you may never solve the puzzle
  • reduce the scope of the problem (roll three dice instead of six)
  • test special cases (make all dice show five)
  • change a variable and see the effect (change one die from a five to a one).

I still end the activity by “assigning” grades based on how quickly a student solved the puzzle as described in the original post.

It was a great first day, and we didn’t spend any time on the computers!

Twitter Mapping Lab


For the past four years, we’ve done a Game of Life lab as part of the Decisions and Loops unit in AP Computer Science. I love that lab for many reasons. However, after four years and not using GridWorld anywhere else in the curriculum, I’ve decided it was time for a change. I’ve wanted to incorporate data analytics and visualization into a lab. After some research and ideas from a couple of labs developed by others, I’m excited to try a new lab this year: Twitter Mapping.


From what I provide students:

Your application will allow the user to search Twitter for a particular word or phrase in tweets located in each of the 50 US states and then display on a map of the US the degree of positive or negative sentiment associated with that search term in each state. For example, if the search term is coding, the following map may be displayed.

Twitter Data Visualization

  • This lab has several goals beyond the immediate concepts of decisions, loops, and unit tests in this unit:

  • Exposure to data analytics. In this lab you will search a large data set (tweets on Twitter) and analyze that data to derive a new understanding (the sentiment of tweets containing a given keyword in each of the 50 US states).

  • Experience using an API (Application Programming Interface) within the context of an unfamiliar software application. In this lab, you will use the Twitter4J API to access Twitter and write code within the partially implemented Twitter Mapping Lab application.

  • Exposure to data visualization. In this lab you will visually represent the average sentiment in a map of the 50 US states.


Feel free to read the entire lab document and check out the GitHub repository with the starter code. If you would like a sample solution, please contact me.


Electronic Lab Portfolios Aligned to AP Physics Science Practices

[Updated 15/7/2016, 10:54 PM: added links to two student lab portfolios.]

As I mentioned briefly in my reflection of the 2014-2015 school year, this past year, students created electronic lab portfolios for AP Physics 2. In summary:

  • many students demonstrated deeper metacognition than I have ever observed
  • several students struggled and their portfolios were incomplete
  • providing feedback and scoring consumed a huge amount of my time
  • structural changes made in the spring semester helped considerably


I was inspired to have students create electronic lab portfolios based on Chris Ludwig’s work and his presentation and our discussion at NSTA last year.

Before the start of the school year, using siteMaestro, I created a Google Site for each student based on a template that I created. I made both myself and the student owner of the site and kept the site otherwise private. The template consisted of two key portions of the site: a Lab Notebook, which provides a chronologically accounting of all labs; and a Lab Portfolio, which is the best representation of the student’s performance. I shared a document with the students that explained the purpose and distinction between the Lab Notebook and Lab Portfolio.

The lab portfolios were structured around the seven AP Physics Science Practices. I wanted students to evaluate and choose their best work that demonstrated their performance of each Science Practice. I also wanted the most critical and significant labs to be included; so, some labs were required to be in the lab portfolio. In the fall semester, I required that each student publishes at least two examples of their demonstration of each of the seven Science Practices.

I wanted students to think more deeply about the labs then they had in the past, and I didn’t want the lab portfolio to just be a collection of labs. So, in addition to the necessary lab report to demonstrate a given Science Practice, students also had to write a paragraph in which they reflected on why this lab was an excellent demonstration of their performance on the specific Science Practice.

The lab portfolio comprised 40% of the coursework grade for each semester. For the fall semester, the lab portfolio was scored at the end of the semester. I provide a few formal checkpoints throughout the fall semester where students would submit their portfolio (just a link to their site) and I would provide feedback on their labs and paragraphs.

Fall Semester

Many students wrote excellent paragraphs demonstrating a deeper understanding of Science Practices than anything I had previously read. Other students really struggled to distinguish between writing a lab report and writing a paragraph that provided evidence that they had performed a given Science Practice. I did create an example of both a lab report and lab portfolio reflection paragraph based on the shared experiment in first-year physics of the Constant Velocity Buggy Paradigm Lab. However, several students needed much more support to write these reflection paragraphs.

In general, those students who submitted their site for feedback had excellent portfolios by the end of the students; those who didn’t, underestimated the effort required and ended up with incomplete or poor-quality portfolios.

What I liked:

  • The metacognition and understanding of Science Practices demonstrated by many students.
  • Students deciding in which labs they most strongly performed each Science Practice.

What I Didn’t Like:

  • Several students struggled to distinguish a lab report from a paragraph providing evidence of performing a Science Practice.
  • Several students didn’t have enough support to complete a project of this magnitude and ended up with incomplete lab portfolios.
  • Providing feedback and scoring all of the lab portfolios over winter break consumed a huge amount of time.

Spring Semester

The spring semester has some different challenges and constraints:

  • We focus more on preparing for the AP exam and less on lab reports.
  • I don’t have the luxury of a two-week break to score lab portfolios at the end of the semester.

Based on these constraints and our experience during the fall semester, I made some changes for the spring semester. I selected seven required labs in the spring semester, one for each Science Practice. Each lab and reflection paragraph was due a few days after performing the lab, not at the end of the semester.

This had some advantages:

  • the portfolio was scored throughout the semester
  • students had more structure, which helped them stay current

and disadvantages:

  • no student choice in selection of labs to include in portfolio
  • no opportunity to revise a lab or reflection paragraph (the feedback could help them in labs later in the semester)

With these changes and students’ experience from the fall semester, the lab portfolios in the spring semester were largely successful. I think it is important to emphasize that both the changes and the students’ experience contributed to this success. I do not believe that the structure for the spring semester would lead to a more successful fall semester. The feedback I received from students at the end of the year was much more favorable concerning the structure in the spring semester than the structure in the fall semester.

Next Fall

I had the wonderful experience of being coached this year by Tony Borash. Tony provided guidance in many areas, one of which was making these adjustments for the spring semester and, more importantly, planning for next year. Together we were able to come up with a structure that will hopefully combine the strengths of the structure in the fall semester with the structure in the spring semester. My goals for these changes are to:

  • provide more structure for students
  • provide student choice
  • incorporate peer feedback

Here’s the plan for next fall:

  1. I choose the first lab. Students complete and submit the lab and the reflection paragraph. I provide feedback. Students make revisions and re-submit the lab and reflection paragraph. We review the best examples as a class.
  2. I choose the second lab. Students complete the lab and the reflection paragraph. Students provide peer feedback to each other. Students make revisions and submit the lab and reflection paragraph.
  3. Students choose the next lab to include in the portfolio. Students complete the lab and the reflection paragraph. Students provide peer feedback to each other. Students make revisions and submit the lab and reflection paragraph.
  4. Students choose some of the remaining labs, and I choose some of the remaining labs. Students complete the labs and reflection paragraphs. Students specify a subset of Science Practices on which they want formal feedback from me and on which they want feedback from their peers. Students make revisions and re-submit.

This past year, students included a link to their lab report in their lab portfolio and shared the lab report (as a Google Doc) with me. Next year, I will have students embed their lab report into the Google site. This will facilitate peer feedback and enable everyone to use comments within the Google site to provide feedback. I may still have students share the actual doc with me, as well as include a link, so I can provide more detailed suggestions directly within the document.

Student Examples


I’m pleased that my students and I are heading down this path and believe my students will gain a much deeper understanding of Science Practices as a result. While I shared this with my colleagues this past year, I also cautioned them that I didn’t have it figured out, and it wasn’t a smooth ride. I think electronic lab portfolios are an excellent way to assess student performance, and I hope that they will be used in other science courses in the future as they are a natural fit to the NGSS Science and Engineering Practices. I hope that after this next year, I will have something that will provide my colleagues with a stronger framework to adapt to their classes.

New Software Engineering Course

[Updated 6/7/2016, 8:08 PM: Added additional security and web app concepts based on feedback.]

After a few years of effort, I’m thrilled to announce that my school district will be offering a new course in the fall of 2017: Software Engineering! As I will explain below, I’m also excited to ask for your ideas.

Course Description

Software Engineering is a weighted, two-semester course for students that have completed AP Computer Science. The course starts with a core set of software engineering topics (e.g., software engineering process; data structures; technology, society, and ethics) followed by a series of software topics selected by students that are aligned to students’ products (e.g., multithreading, networking, security, web apps, embedded systems, mobile apps). After gaining the necessary background knowledge, small groups of students develop a software product as they iterate through software engineering development cycles to produce a software product. Prerequisites: successful completion of AP Computer Science and teacher recommendation.


We have started to work on the curriculum this summer. The plan is for each student in the class to be provided with their own Raspberry Pi. This sidesteps any issues with student not having the necessary permissions on the computers in the lab and enables students to work on their products outside of class. The software engineering process unit will introduce Agile methodologies in the context of a class project, which will also introduce the students to their Raspberry Pi as they develop an audio server. The data structures unit will be significant and fairly straightforward to design. Concepts will include linked lists, queues, stacks, sets, maps, binary trees, hashes, and hash map. The technology, society, and ethics unit will be similar to what we do in AP Computer Science but be concentrated to enable groups of students to focus on a specific topic in more depth. All students will complete these three units.

The remainder of the first semester will be different for each student group. Each group will decide on a product that they want to develop in the second semester. Based on their product, they will complete various modules (probably two) to gain the necessary background knowledge. Due to my background, I’m comfortable designing the networking and multithreading units. However, for the other units, I’m very interested in your ideas as I fear my expertise is either lacking (security, web apps) or outdated (embedded systems, mobile apps). Below, I’ll share some rough ideas for each unit.


Potential topics: cryptography (history, SSL, encryption), authentication (users, servers, certificate authorities), authorization, session management, firewalling stored user data, attack vectors (hijacking sessions, SQL injections, sanitizing user input)

Questions: Cybersecurity is super popular, but so many of the available resources seem targeted at a much more introductory and basic level than what would be challenging for a post-AP class. What topics would be appropriate for these students? What resources are available? What can their explore with their Raspberry Pi?

Web Apps

Potential topics: Javascript, JQuery, MongoDB, Meteor, Bootstrap, PHP, Laravel, open APIs, Chrome extensions and apps

Questions: The last web app I developed was in Perl. What are the best technologies for students to be learning now? I’m excited to learn, and I want to make sure this unit is relevant. What resources are available?

Embedded Systems

Potential topics: bit-wise operations, I/O, interrupts, buffering, ADC, SPI

Questions: How close to the metal can you get on a Raspberry Pi? Which embedded concepts are most prevalent in today’s products? What resources are available?

Mobile Apps

Potential topics: iOS and Android apps

Questions: While Apple and Google seem to have pretty good resources, are there better resources available? Anything else I should consider for this unit?

Group Product

I’m really looking forward to students working in groups for an extended period of time to develop an authentic product. In the context of an entire semester, groups will have time to complete multiple iterations. Ideally, I would love to partner each group with a stakeholder in the community that would benefit from a software product. I have some leads, and if you have any others, please let me know!

Please comment or strike up a conversation on Twitter if you have any ideas.

2015 Summer Reading List

As I was preparing my stack of books for this summer, I realized that I never published my summer 2015 books read. It wasn’t a great summer of reading, but there are a several good books that I want to share.

what if? Serious Scientific Answers to Absurd Hypothetical Questions by Randall Munroe

This should be required reading for science teachers. It is an inspiring example of how to present science in incredibly engaging, although absurd, contexts. I love xkcd and had the pleasure of hearing Munroe talk on his book tour for Thing Explainer which I hope to finish this summer. I include xkcd comics in my slide notes and link to the what if? blog as extension readings in each unit. Sometimes when an AP Physics 2 student is stuck thinking about capstone ideas, I encourage them to create their own “what if?” capstone.

9 Algorithms that Changed the Future by John McCormick

This was a very accessible book. It would be a good summer read for incoming AP Computer Science students. If I ever have to assign summer work, I would consider assigning this book. I may draw from it for the new Software Engineering course that I’m designing this summer.

The Code Book – The Science of Secrecy from Ancient Egypt to Quantum Cryptogrpahy by Simon Singh

This book was fantastic – computer science, history of science, spy craft. I’ve gifted this book at least three times in the past year to family and students, and I’ve recommended it to several others. Singh includes enough mathematics to make it interesting but complete understanding is not required to appreciate the book.

The Housekeeper and the Professor by Yōko Ogawa

A beautiful book. While there is some math, it should be read for the incredible relationship between the professor and his housekeeper. I recommended this book be added to my school’s library.

All the Light We Cannot See by Anthony Doerr

My mom gave me this book and encouraged me to enjoy reading something not related to teaching, physics, or computer science. I’m glad I did. You all are probably familiar with this book; it did win the Pulitzer Prize after all.

Anathem by Neal Stephenson

I am a huge fan of Stephenson. While Snow Crash and The Diamond Age are monumental works because they defined the cyberpunk genre, and the Baroque Cycle is my favorite collection of historical fiction, Anathem is Stephenson’s greatest work. I actually listened to this entire book on CDs (28 of them while driving all over!). Afterward, I bought the book to share with my son and re-read various sections.

[Update 29/6/2016, 11:50 AM] I forgot a book!

A More Beautiful Question: The Power of Inquiry to Spark Breakthrough Ideas by Warren Berger.

I agree with the premise behind this book: questioning is powerful. For me, many of the examples cited were familiar, and, therefore, I found the book not as groundbreaking as I had hoped. However, I know of others who read it and found it quite insightful. If you are a parent, teacher, or business person, I would recommend checking it out from your local library.

My AP Computer Science 2016 Solutions

I shared these with my students and thought that others may be interested as well. I typed up solutions to the 2016 AP Computer Science free response questions. The zip file includes a BlueJ project file and test code to verify solutions. As I tell my students, no guarantee that I wrote perfect solutions and there are multiple ways to answer these questions.

AAPTWM16: Blueprints for Accessible and Affordable High-Altitude Ballooning

Mark Rowzee and I spoke at the American Association of Physics Teachers (AAPT) 2016 Winter meeting as part of Session EI: Quadcopters, Drones and High Altitude Balloons. Our talk was “Blueprints for Accessible and Affordable High-Altitude Ballooning.”

Abstract: We’ll provide you will the blueprints for success since the moment you release your first high-altitude balloon, you are stricken with an unsettling combination of joy and terror. It is relativity easy to launch a high-altitude balloon; it requires much more planning, resources, and luck to get it back. We will share our experiences designing, launching, and recovering high altitude balloons over the past six years. We will share the science that can be done with a variety of student age groups (elementary, junior high, and high school). We will share the materials necessary for a successful launch and recovery for a variety of budgets. We will share the safety precautions that are required. Finally, we have photos, videos, resources, and stories that we hope will inspire you to conduct your own launch.