The STAR project (Student/Teacher Achievement Ratio) was a study done in the United States from 1985 to 1990.
11 000 children were separated into three different groups from Kindergarten to 3rd grade:
– the smaller groups had 13 to 17 students per teacher.
– the medium groups had 18 to 21 students per teacher.
– the larger groups had 22 to 26 students per teacher. The teacher was also helped by an assistant.

The results showed that:
– the smaller groups performed better than the others from Kindergarten to 3rd grade.
– children from minority or ethnic backgrounds succeeded better in the smaller than in the larger groups, and they had a more positive image of themselves and their abilities

What to take from this article ?
It is scientifically proven that the size of the class has an effect on learning: the fewer students the better. And this effect is even stronger for children coming from disadvantaged communities.

References:
ECALLE, Jean, et MAGNAN Annie. 2015. L’apprentissage de la lecture et ses difficultés. Malakoff: Dunod.