It's finally happened
We went straight down there, alternating between worrying about what he had done, and psyching each other into righteous indignation as we had told the school before he started, and as soon as he started, and at parents evening about Mstr A's "issues", but so far no specialists have been involved.
The head was pleased at how quickly we'd come in, and he explained the situation. Mstr A has been sent to him for behaviour 5 times since September. Generally the school will call parents in after three, but considering we had explained Mstr A to them prieviously, and most of the incidents weren't that awful (2 times of "being silly" in the corridor, 1 of spitting (which I knew about) 1 of hiding at the end of break, 2 of physical "attacks" on other students.) neither of the attacks sounded that awful, although we do have a zero tolerance of physical behaviour with Mstr A, because he just doesn't understand how much is acceptable, so it's easiest to say none.
It was quite useful actually - we got a bit more info on how they have been managing his behaviour at school, and we were able to pass on our admiration for the improvement we've seen in his schooling. We also agreed that they should push forward with getting him seen by the Ed Pysch service again and all the associated professionals. Despite the fact that we were very open with the school even before we applied for the place, they still seemed worried about bringing up the issue with us - but once they got over that they said that he showed many of the signs of, surprise, surprise, Asbergers! Both the heead teacher and his class teacher (and his learning mentor) have all worked with aspie children before and were keen to tell us how they can and should go on to great academic careers:-) But it was still depressing that we were called in to the school in that way - especially as i ask Mstr A every day, and he hasn't told me about any trouble since the spitting incident ages ago:-(