In both my calculus classes, I started dreading teaching, because invariably - yap yap yap yap - basically from 1 to 2 boys, but it would affect the whole class in some way. In BC, I sat 2 smart boys together thinking they would work well together. Well, they REALLY worked well together. They started discussing the problems loudly while I was teaching. They would outdo each other to call out the answers really quickly before anyone else had a chance to think - regardless of my constant, "think to yourself quietly / wait 10 seconds before you answer / etc". And when I would speak to them separately, they replied, "but we're learning". They didn't think it bothered anyone else. After numerous complaints, I separated them. Peace. Learning. They still don't think they did anything wrong, regardless of my, "you're not being homeschooled / you're not giving others a chance to learn" comments.
In my other class, the class clown got 3 - 4 other boys yapping, and they're pretty funny (in a nonclassroom situation) and I do like them. However. NOT IN CLASS. Today I moved the clown to the back away from the other boys. Now he's around some studious girls, and for today at least. Whew.
I can put aside my dartboard with their pictures on it for now.