Harry Potter was a smash hit about a boy discovering he’s a wizard and going to school in a magical world full of wonder and adventure. Twilight didn’t hit quite that high a note, but the story of a teenage girl who learns her classmate is a vampire and falls in love with him did quite well. The Hunger Games popularized the dystopian genre with a bow wielding teenager stepping up to survive death games, have angsty romances, and fight the power.
As far as I can tell, nothing has quite hit that same kind of high since and it may be awhile until the next truly big wave. But if it were up to you, what would the next big thing be about?
Please see the Scholomance series by Naomi Novik for a very different take on a school of magic. Basically, young witches enter the school, and if they survive to graduate four years later, they are both lucky and skilled.