Personally with my ds I felt if he'd been able to start part time for a term it would have solved some of the troubles. Unfortunately he was the first year that they brought in all starting full time and no one else was doing part time, and I felt it would be differently bad for him if everyone else was full time and he wasn't.
Just to put a similar incident in: A friend's ds was recently given internal exclusion for similar. They spotted a CCTV camera in the toilets and threw wet paper at it to try and block it shouting "filthy perverts". She did point out to her ds how on earth he thought he'd get away with it seeing as it was being recorded. He was year 8 though.
So similar punishment, but much older.
I would say though, that it may be (as for my ds) they notice that the incidents increase as he gets tired, so it may be that they're not so much excluding him, more saying "actually he's too tired".
How is the teacher handling it? Does she speak to you always, or just when it's bad? With my ds we had a behaviour book and she wrote in round about 6 times a day to say something good/bad/neutral, so I could praise the good, and talk through the bad issues and see his side/suggest what he could have done better. He did usually have some logic why he'd done it, even if it was flawed logic.
And sometimes when talking I felt he wasn't entirely to blame eg one child knocked down his sandcastle every time he built it, so after the fourth time he hit them. Now for that sort of thing I'd talk about how he was naughty to hit, but the other child was also naughty for doing it and I'd sympathise with him how he must have felt. then we'd talk about what he could do which would be better. Sometimes it was walking away; in this case I'd point out that if he'd told a teacher it would be the other child in trouble, not him.
It also means that if there is something going on which is a flash point then they can take steps to avoid it.
I would also just be careful of the school asking you to take him home; because ds would have loved that. In fact he'd quite likely to work out the quickest way to get to be taken home. If you think that might be the case, then it is worth mentioning it to them so they don't use it as a default reaction.