[dkopi]

Actually, smart kids usually end up a net loss for classes. They get bored. so they skip classes, or end up sitting in class bothering everyone else. They also end up frustrating other kids because "why does it come so easy for X but not for me?" Bad teachers even use smart kids as examples: "See, you all should be a lot more like smart kid".

A smart kid isn't going to magically become a free tutor for other kids at school. Let teachers focus on educating. Don't shift that responsibility to teenagers who could be advancing significantly in other environments.

[1stop]

Research shows the opposite. Mixing ability levels increases the median mark. The point of public funded education is not to produce a minority of geniuses but a majority of smart people.

[ZeroGravitas]

I'm not sure whether it happens "magically" or not, but the research is traditionally interpreted to suggest that classes of mixed ability do better on average.