is it possible that your son is merely exploring? I have a 27 mo old son and he still at times throws his cup or fork on the floor. He probably wants to experiment/see food falling.

Or have you tried talking him into not doing it? Probably, if he has already eaten enough, try putting him out of the high chair (after you've talked to him) and see if the freq of throwing food will lessen. Probably, he'll assoc. that if he keeps on throwing food, then he has to be out of the high chair. Just suggesting.

Sherr