It’s 1971, the Source, demons and other various dark creatures have begun joining forces with Voldemort. 

Dumbledore, learning this and knowing there’s no way the wizarding world can’t take them on, contacts his old friend Penny Halliwell and asks if her, her daughter Patty and her four granddaughters the Charmed Ones could come to Hogwarts. 

(Paige’s adoptive parents died when she was six and Patty and Penny basically decided screw the Elders and took her in, also their powers were never bound).

Patty also contacts her old friend Bobby Singer (they met on a hunt a few years prior and surprisingly he didn’t kill her where he stood) and requests that he send Dean and Sam Winchester (whose father left them with Bobby to go chasing the demon that murdered their mother) to Hogwarts as well so the wizarding world can have hunter knowledge and also the boys can learn not every supernatural is evil.

And to her shock, he agrees.

When the five arrive at Hogwarts they don’t particularly care about house rivalry and befriend whoever they want (Paige, in particular, befriends Regulus and tries to steer away from the dark ways of his family)

Paige and Sirius hate each other initially but quickly become close and later fall in love yet are so hopelessly oblivious/in denial that everyone at Hogwarts (including the Slytherins) just want to bang their heads together.

(Phoebe and Remus are briefly like this but do get together). Prue and Sam, plus Piper and Dean are equally as difficult.

Sadly Penny and Patty are murdered by Voldemort and the Source the summer before third year but the girls are taken in by McGonangall who’s like their aunt. 

(Sadly this means she has to put up with the marauders out of school).

The five aren’t technically students given that they either have no magic/their magic is different than what the school teaches, however, the Charmed Ones are able to cast spells wandlessly and they also teach the students basic combat, spell creating and potions that the school doesn’t teach.

Dean is 16, Prue is 14, Piper and Sam are 13, Phoebe is 11 and Paige is 10 when this story would start