I like this a lot, except I'd be cautious about using "good" there. I know some anxious students who would feel like they were automatically bad at math because they couldn't do all that yet. Maybe "I have mastered the math concept when.
grade math anchor charts - 51 math anchor charts to help teach your students key math concepts. Anchor charts are a great addition to your students interactive math journals or a great reference tool to post on your classroom walls.