Grouping students in this manner can lead to a 'self-fulfilling' prophecy of low performance. The results is in an achievement gap that is often permanent and irreversible. A teacher may separate his or her students into groups based on their achievement levels, usually for reading and math. An elementary school may also do between-class grouping, separating students by perceived achievement level and placing them in a class for all day instruction.
Middle schools are more likely to practice between-class grouping.
Schools that utilize a block schedule will keep students together throughout the day as they change classes. High schools that group for instructional purposes use a varying form of between-class grouping, often referred to as 'tracking'. Students rarely have an opportunity to move up from the 'track' into which they have been assigned. There IS evidence that Tracking and ability grouping provide unequal educational opportunities and outcomes. Instructional grouping is a primary mechanism for the resegregation of schools by race and socioeconomic class.