I think it is pretty open/shut that these are his photographs and his property.
That said, the school probably has a leg to stand on when it comes to protecting the privacy of it's students at school activities.
It would be a reasonable general rule (that should be enforced as such and not just applied to one person) that you cannot publish photos of students on the Internet taken at school events. They can presumably enforce this for students but they would presumably need to also enforce a "no photos" policy at games/etc with the parents (i.e. in order to attend the game, you must sign this waiver).
If student privacy is the real issue, then they need to follow this through all the way. Half measures seem less likely to be enforceable or even useful...