A cynical perspective: schools are prisons, and some lower income gang-joining students are criminals. An extra hour in school corresponds to a criminal spending an extra hour in prison instead of out wreaking havoc. The next question is forcing such students to stay in the school to begin with...
I think "schools are places that give people of a certain age something to do without giving them the option of leaving" is a perfectly valid sentiment and a good description of why more 10 - 14 year olds would perform less crime.
Calling them prisons implies the entire population of students would commit said crimes.
