**This page is under construction**

**Also, keep in mind that this page contains spoilers for the game. If you want a spoiler-free version of the game, get in touch with me. We can play via the web in 30 minutes with as few as 3 people and you’ll learn more than this page can tell you.**

I’ve been developing a game for analyzing student work, in collaboration with Justin Reich and his lab at MIT — it’s called Baldermath. The intended audience is for either pre-service teachers or professional development. This page contains everything you need to play the game with students or colleagues on your own.

(We’re still testing, revising and trying to better understand the game. I’ll try to keep this page as up-to-date as possible.)

How to Play Baldermath


These rules are mostly still true, but there are two things missing from the current version of the game.

An important change that we’ve made to the game is that the judge does something while the other players are creating their student work. Specifically, the judge tries to anticipate (for points!) the student work that the other players will create for the problem.The judge gets two copies of the problem and gets two tries to anticipate an idea that one of the other players will create. (Without this, it feels as if the judge doesn’t have the same chance to think about student work that the players have.)

The other missing info from these rules: when the judge picks up each piece of student work, the creator of that work gets a chance to explain what the student “did” in that work.

The Thought Behind the Game, In Brief

Many researchers, teacher educators and professional developers have proposed that student work analysis could be a promising arena for teacher learning. They also are unanimous that what feels “natural” for many teachers to focus on in student work is not always productive for learning or teaching. Artificial constraints — imposed either by oneself or by a facilitator — are very important for making sure that talk surrounding student work.

Could a game provide some of those constraints without the heavy hand of a facilitator? And could we have some fun in the process? And could the experience help set the stage for internalizing some of the constraints that experienced teachers impose on themselves while looking at student work? These were the questions that we aimed to investigate with this game.

How I Run a Baldermath Session

I usually start by just handing each group of players a piece of student work and giving them a deliberately vague prompt: “Take turns sharing a thought about the student work.” This is intended to provoke people to act “naturally” with the student work. I do this so that I have a sort of baseline when comparing the way a group naturally talks about student work and how they talk about student work within the context of the game. (“Does the game change how people talk about student work?” has felt like a crucial question for us to understand, as designers.)

At that point, I share the instructions. (It also really helps people to understand the rules of the game if we explain them in context of a piece of student work. This is another reason why it’s important to start with a piece of student work analysis before diving into the game.)

Then, we play the game. Here are the materials you need.

  • Everyone needs a copy of the student work to analyze before the game begins. Here is the student work I’ve been using: WORK.
  • Everyone needs to see the instructions. Here is our work-in-progress version of the instructions: INSTRUCTIONS.
  • Everyone needs something to write with. Here is a link to pens: PENS.
  • Everyone needs a blank copy of the problem. Here is the blank I’ve been using: BLANK.
  • The real student needs a copy of a real student mistake. Here is the student work I’ve been using: REAL

That’s all I can share for now. Grab any other mistakes, from this site or elsewhere, and you can play another round of the game with that.

Have fun!

Is it fun? 

People seem to have fun while they’re playing. Here are some pics people shared of their experience of the game.


I usually ask people two questions after playing the game:

  • What was it like to play the game? What were you thinking about?
  • Any ideas on how to improve the game?

If you play the game, I’d love to know how people you play with answer these questions.


Here are some papers that I think a lot about while working on the game:

Little, Judith Warren, et al. “Looking at student work for teacher learning, teacher community, and school reform.” Phi Delta Kappan 85.3 (2003): 185.

Ball, Deborah Loewenberg, and David K. Cohen. “Developing practice, developing practitioners: Toward a practice-based theory of professional education.” Teaching as the learning profession: Handbook of policy and practice 1 (1999): 3-22.

Kazemi, Elham, and Megan Loef Franke. “Teacher learning in mathematics: Using student work to promote collective inquiry.” Journal of mathematics teacher education 7.3 (2004): 203-235.


If you record your students or colleagues playing this game and send it to me I would be eternally grateful. My email address is michael@mathmistakes.org.