Here's an idea: just make senior skip day an official day off for seniors. Just call it Senior Holiday. 12 graders don't have school that day. Police know to expect increased activity at the beaches or parks. Local restaurants and theaters get some patronage. Teachers with 12 grade classes can catch up on stuff like grading. We went through the same thing with skateboarding in the 90s: the solution was to build a fucking skatepark. You don't prevent teens from being teens, you create a safe environment for them to be teens.