Consider this scenario. A third-grade teacher is about to begin a math lesson on finding the missing side length of a polygon when the perimeter and the other side lengths are given. She has taught perimeter over the last two days, and her lesson plan is ready. What she does not yet know is whether her students can still determine the perimeter of any object when given the length of all sides, whether they can add and subtract well enough to work with those numbers, or which two or three students will need her attention first once the new content begins. Without that information, she will find out the answers later, like in the middle of the lesson, or on the unit test, when it’s too late to help her students in the moment. Effective checks for understanding come from strategic planning, beginning with what you want to test students on and ending with data gathered from every student about what they have learned and know from the lesson. The Model Teaching Math CFU Lesson Builder is a free planning tool that helps create a detailed plan to check for understanding in a specific lesson, aligned to your lesson objective or standard.