My DS5 is in K and we just do EPGY at home. He goes to 1/2 day K so there isn't that much time in his day to be able to do it there (and I'm not sure they'd let him anyways). In fact he still has to do his K homework even though they know he is doing 2nd/3rd grade math at home. (He's into 3rd grade in EPGY - he started at K lvl mid Oct)
I'd love to hear if anyone has been successful with using it at school. Even though I think his only option would be during computer lab time (1/week) it might be better than nothing.