[wrp]

Collecting problem children in smaller, more controlled classes is the only effective strategy. In a class of say, 30 kids, it just takes one to disrupt a lesson. On the other hand, if every kid is cooperating, a single teacher can effectively manage a class of hundreds (and actually do in some Asian countries).

Separation helps the problem kids as well. I have personally observed a high success rate in turning around kids once they get the more focused attention possible in a small class.

To be concrete, if you had 2 teachers and 60 kids with 5 of them "problematic", the most effective approach would be to divide them so you had the 55 cooperative learners in one room and the others in their own class.