This is not a characteristic of boarding schools which your teenager will consider terribly important. But it was a huge plus for us parents. We had spent many years raising our children according to our personal values and precepts. When it came time for our young adults to begin to leave the nest and fly solo, we still wanted the reassurance of a safety net. 24/7 supervision is something which boarding schools simply do very well. They have looked after teenagers for decades. They are tuned into what goes on in those young minds. They have the safety net at the ready. The net is invisible most of the time. But it is there when needed.
Boarding schools know how to handle the hormone factor before things run amok. They understand bored teenagers. And they do all of this unobtrusively most of the time but conspicuously when that approach is called for. We didn't want to worry about who was driving our daughter home. We didn't want our child going to somebody's home where the parent was either not at home or was disengaged from parenting. Boarding schools' 24/7 supervision was a feature almost as important to us as the impressive academics were.