Learning how to FIGHT TO THE DEATH with offensive magic is an after school activity for a group of twelve year olds. Sure, Harry had to find a way to learn the disarming spell that he would eventually use to defeat Voldemort, but Dumbledore and the others were, like, totally chill with having the second-years know to maime each other with fucking witchcraft and snakes and shit? So not good.
Hogwarts kids spend most of their time in their dorms and common room with basically no supervision, except for the prefects, who, even though they were the top students, were still just a couple of seventeen year olds who were probably off in their special private bathroom giving eachother sexually transmitted magical maladies. Wait- wasn't Ron a prefect while we was spending a good majority of the sixth book playing Tonsil Quidditch with Lavender fucking Brown? Damn, kids could have died.
How many times does it mention them drinking firewhiskey? AT SCHOOL? Not to mention the access they have to that entire range of potions that are basically psychoactive drugs. I mean, one time Harry takes that Felix Felicis, which, judging by it's effects, is pretty much Ecstasy, and then goes and gets drunk with his teachers. Then later, Ron gets poisoned, when he's getting drunk with one of his teachers. And everyone's like, "Thank god Harry knew the antidote!", instead of "We should fire Slughorn."
No magic in the hallways, no magic outside of school, no sneaking out after curfew, no permission to leave campus unless its the weekend AND you have the signature of a parent/guardian. These are all rules at Hogwarts, the breaking of which are consistently essential to the plot, and usually, they're rewarded for it.