Although the ability-grouped students learn the same amount as those students who are in mixed ability classes, there are a number of positive and negative effects between-class ability grouping has on the students and their teachers. This type of grouping has a more positive effect on the high level students. "It is known that the top 10 to 15% of these students benefit from this grouping" (Considering Individual Differences). For those students in the middle and lower levels, there is no proven effective change in their achievement level. Because of this problem, the achievement gap between high and middle to lower level students is now wider than before.
In pertinence to certain subjects such as reading or mathematics, between-class ability grouping can produce greater achievement gains than mixed-ability groups. However, a common problem with between-class grouping is that the students in one group have little or no contact with others students outside their group. Yet another problem they are faced with is "teachers' expectations and the quality of instruction are often lower