The streaming of students by ability is harming overall education standards, according to new research from the Economic and Social Research Institute.
The institute says that students in lower streams tend to perform much worse when grouped together.
It said students assigned to higher ability classes do not make corresponding gains - so average student performance falls.
The review says the majority of schools stream students for at least some subjects - mostly Maths, Irish and English.
The ESRI review also points out that teacher-student interaction is crucial to student outcomes and international evidence shows that ''teaching methods matter''.
