If they'd cut out their classmate's head from their yearbook photo and pasted it onto the body of a pornstar with elmer's glue would police have gotten involved? This type of bullying is as old as dirt. Bullies suck, and the kids who did this should get in some kind of trouble with the school and their parents, but this is not something police need to be involved in. The moral panic over deepfakes is ridiculous, but…
You don't see a tangible difference in the detectability of the fake being a factor? The glued on photo will always be uncanny, but deepfake will not.
Eh, this is still a civil matter. Unless the picture was made for the purpose of harassment, there is no ill will we can presuppose the perpetrators had towards the victim. Just immense immaturity and a lack of judgement and empathy. Judgement and empathy can be taught. (If it was done with the intent of causing distress, i.e. cruelly, it's a matter for the police.)