Ability grouping, or tracking, is the practice of separating students into achievement groups and tailoring their curriculum accordingly.

Ability grouping became widely used in American schools of the 1920s as an influx of immigrants entered the school system. IQ tests were administered to determine the ability levels of students, who were then placed in programs that matched their scores. Low-scoring students were given instruction that would prepare them for vocational or unskilled labor, and the high scorers were given college-preparatory work.

Tracking is still the standard practice in most schools in the United States, although current tracking tends to place more emphasis on separating the slower learners from faster learners. Students who need more attention—either because they have trouble keeping up with their schoolwork or because they are ahead of the class and need extra stimulus—are separated and given a curriculum more suited to...