Wow, reading through the responses, my advice/story is vastly different!
My son is nine now and in fourth grade. He is very bright and started school early (he was two days off the cutoff, so not really drastic but he's still the youngest in his class).
He always excelled at every activity and is a really curious child and loves to learn. We knew he would love school, we anticipated some talking issues but never anything else. Then he started first grade. Multiple tripsto the principal, notes home, conferences with his teacher - how could our straight-A son begetting in this much trouble?!
We never had his evaluated or tested or anything. We were also very lucky to have a wonderful teacher that year who worked really well with us.
So, on to your post. :)
Does he have any consequences at school for getting in trouble? Mine would miss recess and while it was more of a disappointment, he didn't really seem to care, at least it was something and it was consistent.
Also, are you notified when he misbehaves at school? We had assignment books that listed the color he was on each day. Partway through the year he was also given a behavior notebook that he had to write in each day. It said what color he was on and if it was anything other than green, he had to write out why. He and one other boy in his class were the only ones who had these notebooks and he hated it. He and his teacher worked out a timeline of consistent good behavior that would allow him to stop keeping the notebook. He eventually met that goal and was thrilled when he didn't have to keep the notebook anymore. Of course, several days in a row on anything other than green and we would talk about whether we'd have to start the notebook back up again and that was usually enough to get him back on track.
He struggled his whole first grade year with disruptive behavior. Usually keeping his hands and feet to himself. Each year he has improved and halfway through his fourth grade year, I believe he's been on green all but a couple days on yellow for talking out of turn.
We have also always been realistic with our goals for him. A day on yellow here and there we always make sure we talk about, but there are no consequences (unless it's a serious action which would usually jump him more than one color anyway). We don't expect him to have a perfect day every day and we talk a lot about effort and respect, the two reasons he should behave in school.
We've also always been able to reason with him pretty well and he learned very early on that nearly every choice he makes is ultimately his own. If he doesn't like missing recess, then it's up to him to make the right decisions that keep him out of trouble.
We've also talked about how it's much easier and more pleasant to follow the rules and stay out of trouble than to do the things that cause him to receive punishments.
We did rewards at home for consequtive days on green and that also helped.
Hope something helps. I definitely feel for you. It's disturbing and embarrassing to deal with. But there is hope!