Mr. Todd teaches third grade. Each day, from 1:00 to 2:00 p.m., his students and another third grade class practice math together. There are two groups, each one a combination of Mr. Todd's class and the other class, and the groups are based on math ability. At 2:00 p.m., all of his students return to his class. What concept is this scenario most closely depicting? between-class ability grouping regrouping combination class within-class ability grouping