gcvmom, what used to worry me about this scenario with difficult child 3, was - when they said, "We'll get the story ourselves form difficult child 3," it actually meant, "We will interrogate difficult child 3 and make him see that he must have been mistaken; we will so muddle and confuse him that nothing he said can be believed."
One classic incident (there were many) had a witness at last. This covered incidents in a very short period, while difficult child 3 had a close buddy who also visited at our home every afternoon. That kid moved away after a year. But this incident - the pack of little thugs which we KNEW were a problem, had attacked difficult child 3, deliberately tripping him so he fell onto rocks and came home with bloodied knees. His mate saw it all and told me. difficult child 3 came to me (unprompted) when he got home and said, "X and his friends were hassling me; X tripped me up then they laughed. My knees were bleeding." His mate said to me quietly, out of difficult child 3's hearing, "They are a real problem, they hassle difficult child 3 all the time."
I wrote a note to the teacher, especially incensed because difficult child 3 as always getting into trouble for things he was allegedly doing to this gang of boys when I knew it was difficult child 3 defending himself, or hitting back after being provoked. Teacher's response - he interrogated both boys (difficult child 3 and his mate, the witness). He also interrogated X and mates, who all said, of course, that they were nowhere near difficult child 3 but they had seen him trip over his own feet as usual. difficult child 3 came home that day saying, "I could have sworn it was X who tripped me up, but Mr K says that because I'm autistic, I don't always see things as they really happen. I didn't know that. He said I must have been mistaken."
I turned to the mate, the witness - he looked scared and would not talk about it. I think X and his mates had got to him and it was the last time he told me anything about what was going on. They moved a couple of months later, I think his mother wanted to get her son out of this school.
So when teachers question your child, do not trust it if your child's story changes as a result. Ask your child (very carefully, so as not to prompt) what he believes happened and what was said to him.
And any witnesses you have among other kids - protect them. They are gold. If you suspect that any teachers will "out" them or make life difficult for them, never reveal your sources. I found I did a lot better with keeping teachers behaving themselves, if I reported an incident but did not reveal which kid had told me. Even if the school later said, "That did not happen," I did not mind because I knew they would make sure it did not happen AGAIN. When challenged as to why I would not reveal my sources, I described the incident above and said, "I will reveal my sources when you have a witness protection program. Not before." Say it with a grin perhaps, but mean it.
Perhaps I'm a bit too jaded, but even though I live in the same town as these teachers, even though we happily chat when we meet at the shops, I could not trust them to protect my child, not if that aim clashed with CYA.
Marg
I seriously wanted to lay into the band teacher at last night's back-to-school night. But I realized that was not the appropriate venue for such a "conversation" and my emotions needed time to settle since it had only been 90 minutes since I'd found out. 
Sometimes I just don't get the way he thinks!
