Jen,
The one thing I found really helped my younger son was getting put in the classroom of a teacher with a very even keel. He has been in classes with nice teachers before, but when he would act up, or start working himself up, the teacher would get stressed or upset and DS7 would find himself being unable to calm down. The emotional levels would just keep climbing.
This year, he has a teacher who admonishes him when he's bad, praises him when he's good, but does not take his behavior personally. He is thriving. Because she does not react to his behavior with any strong emotions and she helps him think about his action, he has been calming himself down quickly and had very few issues.
I don't know how well this will work with other children, but that is the only experience that I can point to that has helped a lot.
