I did not realize this board was made up of so many perfectly disciplined former youth.

I'm thankful that where I grew up, parents and schools knew the difference between criminal activity and youthful pranks.
You get caught pulling a prank off campus, the parents get involved; on campus, the school and the parents get involved.
Cops should not get called for pranks, no matter where they occur.

As far as a coach's jurisdiction, it does not extend beyond the school and the practice field. These are not professional athletes who are being paid to play. That would be more equal to any full-time employment, where if you mess up outside of work, and it reflects negatively on your employer, you get fired. These are kids in an extracurricular activity.

Coaches, Band Directors, Drama Teachers, etc., don't have special disciplinary privileges that extend beyond their roll as the organizer of an activity.
If something happens during school or practice, the coach should handle it, along with the parents.
If it happens outside of school or practice, it is the parents responsibility.