Ability grouping, also known as tracking, is the practice of grouping students together based on their talents and achievement levels. There are two main types: within-class grouping which puts similar students together for certain subjects, and between-class grouping which separates students into different classes or course levels. While ability grouping aims to better suit instruction to students' needs, it can have negative effects like mismatched placements, racial segregation, and lowered expectations for some groups. Recent reforms focus on detracking by creating heterogeneous classrooms and emphasizing collaboration between all students.