I don't think the father acted responsibly. What he did in front of other minors at school was wrong. He was lucky he only busted this kid's face up a bit. What if his blow had caused an aneurysm? What if he knocked the kid to the pavement and caused brain damage? Would it still be sensible then? Would the courts justify manslaughter because a 17 year old slept with a 15 year old?
Prosecute the kid for statutory rape under the law. Prosecute the dad for battery under the law. Let both of them take responsibility for their actions.
I actually think the father went too far, but I don’t think he will serve time. If the 17 year old had been seriously injured then the dad would probably serve some time, but two stitches and some bruises probably won’t bother a jury too much.
This will be plead down to some type lesser offense and the dad will be sentenced to probation and community service. The 17 year old will probably never see any charges at all because these cases are difficult to prosecute also.