Don't hire him!
Make him work as an unpaid student assistant, with his other option being getting kicked out of school.
That way you can give him all the crap work like cleaning up from stupid hackers (and make sure he knows he has to get approval from someone else before running a script he's written to "help" him with mundane tasks, lest he take the mainframe down again) and if he turns out to be bright and has reformed his ways you can offer him a paid job after he graduates.
Biting the hand that feeds IT
