If the parents of the students participating in the game haven't signed a release to have their pictures taken, and someone is taking them, then the school could have major legal issues. At our school, staff and volunteers are banned from taking anything home that has children's names on it like seating charts, absent logs, or even track schedules. It has something to do with the kids being minors.
No, it has nothing to do with the kids being minors, it has to do with FERPA, the law that is the education analog to HIPAA. It protects education information. It does not affect playing sports in a place anyone can see. Similar to how HIPAA protects a doctor disclosing your medical information, but it doesn't protect somebody else seeing your car in the parking lot of the doctor's office, or exercising in a public park even if it's because the doctor advised exercise, or even another patient posting on Facebook that they saw you in the office. Photographs of students participating in athletic events in view of the public is most certainly not FERPA protected information.