Hi L.,
I know people will tell you that "it's a boy thing," but actually my 4 year old daughter has always been VERY high energy, athletic, excitable etc! I learned a lot from the preschool that she went to last year - it was a Carden School, which was founded by Mae Carden in the 1920's and to this day they follow her principles. Basically, she was a huge proponent of holding kids accountable for their behavior, and expecting nothing but the best behavior at all times. I know, you're probably thinking, "Have you MET my kid?!" - but believe me, my daughter was a DISASTER prior to going to this preschool (5-10 knock-down, drag-out tantrums a day at her previous preschool, to the point that they kicked us out), and now she is in Kindergarten and the best-behaved child in the class.
What I observed at the Carden preschool was that they strictly adhered to a schedule at all times. For instance, if the routine was to come into the classroom quietly, sit at the table, and play with counting blocks until class started, then they NEVER deviated from that. Ever. In this way, each child knew exactly what to expect. They had snack at the same time every day, recess, naptime, etc. They really frowned on tardiness, and in fact if you showed up and they were already doing the flag salute, you had to go to the school office and get a permit slip to go to class. So pretty much we all learned as parents to get there 5 minutes early NO MATTER WHAT. This seems like something small, but the strict routine really helped my daughter.
Also, if she misbehaved, the teacher would say very simply, "Isabelle, we do not hit other children." And sit her in the corner (where she could cry or whatever, but she had to stay there until her time out was over). If she came out and hit again, the teacher would repeat the exact same thing, "Isabelle, we do not hit other children." and right back into the corner she would go! Well, after about 3 days of that, she got really tired of sitting in the corner, but she knew because she got the exact same response every single time without fail, what the consequence would be, and she stopped her bad behavior. Honestly I was shocked at how quickly the turnaround happened with consistent and simple discipline.
Likewise, when giving instructions, they would give the exact same instruction. For instance, if the kids were to color all the circles on the page, the teacher would say, "Use your crayon to color all the circles on the page." If the child raised her hand to ask what they were supposed to be doing, the teacher would repeat, "Use your crayon to color all the circles on the page." NOTE: I always figured if a child asked a question when I had just given instructions, it was because I hadn't explained it well enough. Not necessarily so! Kids' brains are wired differently from adult brains. Literally it can take 4 or 5 times of saying the exact same thing for it to sink into a child's brain. Don't muddy the waters by giving tons of explanations - just repeat exactly what you said, patiently, over and over until they get it.
I know that doesn't sound earth-shattering, but it really did work for us. My daughter went from being an absolute nightmare of a kid (her own grandparents refused to babysit her, I am not kidding!) - to being under control and able to handle herself. It takes a joint effort from you being VERY consistent at home at all times, and the teachers doing the same at school. They cannot allow him to misbehave at school at any time (nor can you at home), and if he does, the consequence needs to be swift and consistent so he learns what will happen AND what is expected of him. If the school cannot or will not do this, then you should try to find a school that believes in self-control and discipline. Some kids really need it.