he's gonna get fucked up in prison, no doubt. however, it won't be just because some other inmate has a daughter/neice/cousin/conscience. it's more about power and control than anything else. it's definetly going to be the longest 15 months of his life, but it should definetly be a longer sentence.
it doesn't say (or i missed it) if he's going to juvenile or adult prison. chances are he'll go to a juvenile facility considering he was 15 at the time it occurred, or could quite possibly go to a juvenile facility for a while and at his first fuckup, he goes to adult prison. the laws are weird on stuff like this and it varies from state to state. typically what i've read and researched is that if the crime was committed as a juvenile and the juvenile courts handled it, the offender won't go to an adult prison. but like i said, it all varies from state to state.
just because he was a high school football player doesn't mean he can handle himself. not all high school football players are huge guys. the team my senior year of high school went to (and lost) the state finals. they weren't huge and while they were pretty tough i'm sure none of them could hold their own against 4 guys in prison.