I may be working off of a lack of details here, but there's a good chance that the town this school was in had plenty of churches nearby. If 16/17 year old kids are old enough to make their own decisions, then let them walk into church on their own time and get baptized if they so choose.

Why the hell is their football coach rounding them up on a bus to go do it? It just sounds like he's purposefully trying to use his authority to get the kids baptized, with further evidence being that he did it secretly. A football coach or teacher has no right meddling in the personal lives of the students, be it a religious situation or otherwise.