Why I built Mistake Master

I kept seeing students make the same kinds of mistakes. A wrong answer often tells you much more than whether a student understood the question — if you know why they chose that answer, you have a pretty good idea of what they need help with next.

Last updated: August 12, 2026

So I started organizing questions around the misconceptions I was seeing in my own classroom. That eventually turned into this site: free, browser-based practice where every wrong answer choice is tied to a specific, named misconception. Most practice tools tell you what you got wrong. Mistake Master is built to tell you why.

How it works

You start with a short diagnostic on a topic. Each wrong answer is tied to a documented misconception — the research on how students learn these subjects has catalogued them well. Instead of a generic "review everything" prompt, you get a list of the specific ideas you need to work on, with practice aimed at exactly those.

Eleven courses are live: AP Physics 1 (all eight units), AP Physics 2 (all seven units, numbered 9 through 15 so a unit number means one thing across both algebra-based courses), AP Physics C: Mechanics (all seven units), AP Physics C: Electricity and Magnetism (all six units, numbered 8 through 13 as the College Board numbers them), AP Chemistry (all nine units), AP Biology (all eight units), AP Precalculus (all four units), AP Calculus AB (all eight units), AP Calculus BC (all ten units), AP Statistics (all five units of the redesigned 2026 course), and SAT Math (all six domains). Every course has lessons, interactive labs, diagnostics and cumulative review. The approach is subject-agnostic by design.

For teachers

Teachers can create a class, share a join code, and see a gradebook that groups misses by misconception rather than by score — so you can tell which ideas need reteaching across the class and which students to pull for targeted support. There is a dedicated teacher hub with field notes on the most common misconceptions and how to address them.

What it costs and what it collects

Mistake Master is free. Students do not create accounts to practice, and the student-facing tools run entirely in the browser. For specifics on data handling, cookies, analytics, and the domains the site loads, see the IT and privacy review page.

That is where the name comes from. The mistakes themselves are the useful part — once you know what a wrong answer is telling you, you know what to work on next.