Both sides have a point. I think a good teacher would have indeed separated this unusual entry from the main competition, because the other kids would have re

Both sides have a point. I think a good teacher would have indeed separated this unusual entry from the main competition, because the other kids would have reasonably felt cheated by competing against something that's more a ball than an airplane. On the other hand, it's a clever hack, and deserves some acknowledgement. The appropriate acknowledgement depends on the kid; I know that if I did something like that, I'd probably either have some mischief up my sleeve or just want to disengage from the task as quickly as possible. The best way to have dealt with me, then, would be to acknowledge that I've got a clever trick, but that with all my spare time I should really construct something that has wings and flies, in the (implicit) spirit of the event.