I'd be getting pretty firm and clear with the staff that they need provide more answers and plannin and they should be protecting your son more. Once in a while, yes, these things happen and they can be difficult to foresee and prevent. 10 times in a year... that's a pattern and I'd tend to guess it's the same kid who should be a) being more closely supervised and b) helping him/her address whatever's driving the biting. Fine, don't tell you who it is, but they ought to be more forthright on the situation so you can make decisions about your child.