in the US, at least, you can, but there are a bunch of limitations and rules. You (the kid) have to get a 'work permit' and can only work certain hours.
I got my first long term job at 14, and I had to go through rigmarole. it was pretty irritating; my mom made me quit my first job before summer was up because they didn't have the right paperwork and workmans comp, etc... Sure, i was being "exploited" as she said, but it was a very positive experience... and I got cheap used computer parts from that place for the next three years.
However, in this case it is properly the only course of action:
Can you even legally hire a 15? (no matter if he is still in school, we all know how valuable hs is).