Here’s the idea for this site:

Teachers need to be able to quickly look at mathematical work and identify the assumptions behind the work, and what actions to take in response to the work. That’s hard. But practice can help us get better at this.

The idea is that on this site each post will be a selection of student work. That student work will be posted by me, but sent in by you. And then in the comments we’ll discuss: what are the assumptions behind this work, and what could the next steps be.

To submit to the site, email me at mathmistakes@gmail.com.

Also, we tag everything, so check out the bottom of the page for the labels. In a year we’ll have amassed and tagged hundreds of math mistakes, so this site will become a valuable resource for planning lessons.

Enjoy! Be in touch if you have any comments or suggestions.

[…] Math Mistakes – Michael Pershan put together a website which aggregates math mistakes teachers have found so we can collectively analyze them and determine what is happening conceptually or procedurally that would lead to that conclusion. This problem has an especially enlightening mistake that shows up in the second comment. […]

[…] Pershan’s fabulous new (in addition to his insightful “regular” one) blog, Math Mistakes where readers are faced with the tasks of identifying not only “what don’t they […]

Kitsays:

This is such a cool idea! I’m going to share it with my colleagues!

Renata Relyeasays:

I am actually thinking about using this with students and see if they can spot the error. This would be a wonderful learning tool to have practice with explaining their answer; deciding if an answer is reasonable or not as well as developing their critical thinking skills.

Raelynn Kershnersays:

Using with students is such an excellent idea! Our test data indicates we are weak in this kind of analysis. This is a great source of material!

piasays:

I respectfully disagree- I think that would be most unfair to ask kids to untangle another kid’s scrawl, in fact my instinct says this would turn them off forever – plenty of other ways to get them to reason and problem solve.

It would help if each submission specified the grade in which each problem has been given.

This is a nice site. I’m going to add it to my blogroll.

Georgesays:

This is a great site. I teach education courses and am going to use this to illustrate the complexities in student thinking and understanding. Now that I know such a site exists, I’ll be sure to share interesting examples of student work when I come across them.

Daryl Stephenssays:

I plan to use this site with my secondary math methods course when we talk about giving effective feedback to students.

Hi Michael,

This is an amazing concept! As an educator and tutor, I’ve personally learned so much through my students’ mistakes about how to avoid common pitfalls and fuzzy thinking. This gives students a chance to step into our shoes and get a fresh perspective on how to do mathematics in a very non-threatening way. (I’ve also found that students like to correct each others’ mistakes lol).