Small numbers...

In any class there is spread in abilities of children. They fall in three broad categories 1. Above average, 2. Average and 3. Bellow average.

In a smaller-sized class, the difference in their abilities stands out markedly. And there are small number of students in each of the three categories. This makes it harder for a teacher to adopt a single strategy which works for all. Any strategy will discount at least two of these three group of students.

In a large class, the number of students in the average category is large (middle of the Bell-curve) compared to those in the other two categories. A teacher can adopt a strategy which benefits maximum number of students; those in the middle of the distribution.

Thus I think the size of the class affects quality of learning (and teaching) and interestingly bigger class sizes may stand to benefit more. At least this effect is counter our perception of smaller the class is better. Obvious question is, What is the optimal size of a class for a teacher with given resource, time and ability, so that maximum students can benefit without compromising quality ?

PS : I don't imply that one should leave out above and below average students. We do need to challenge the above average students and give additional help to the bellow average students. But a single teacher can't have three strategies going on at the same time in a class.