They're probably afraid that having their sons questioned will be very distressing for the boys, but fortunately I believe this is actually a crime that can be pursued automatically. They may also be afraid of retribution from the jocks or their parents, because in a lot of these places, no matter what the jocks do, it's cool.
That said, I think this goes way beyond hazing, and the older students should be charged with sexual assault, along with the adults who set them up to it.
The description seems to indicate local police and the school district are desperately trying to avoid actually charging anyone with felonies.