This sounds EXACTLY like my 8 year old daycare boy! Thanks goodness, he is only mornings (and full day PA days). But I to, am at my wits end with him. And the parents are the same as the ones your describing. The acknowledge the problem, but do not take steps to fix it.
Whoa! See at 8 years old, i know for a fact that they know better than to behave like that. I don't know how you can put up with it. If it were me, i think i would let him go.