We've had this argument already but we still can't have 7-18 year olds roaming around with no education looking for something to do.
Children aren't evil per se but the first thing they do if you let them is they try to disrupt as many things around them as they can. And if they find something to disrupt, they go "great! I wonder what else I can get away with." They're not malicious - they're exploring their powers and finding their personalities - but if you let it grow into maliciousness, it absolutely will.