How much are students actually learning in our classes? The best predictor of a student’s final exam grade is how much content knowledge they had coming in. This prior knowledge can be assessed with a pre-test, allowing instructors to adjust the course based on what students already know or don’t know. The instructor can use the pre-test scores to create student groups that are either heterogeneous (for cooperative learning) or homogeneous (for differentiated instruction) with respect to content background at the start of term. A curriculum designer wishing to compare learning gains for different teaching tools such as cooperative learning could assess sections of the same class using different curricula with the same test.