Sorry but Reverend Insanity is the most unique novel in novelupdates. Finding another one like it is like finding a needle in an entire ocean. I suggest you lower your criterios.
I don't recall school life in Reverend Insanity. But if you want an evil protagonist, I recommend Ouroboros Record Circus of Oubeniel, Dungeon Defense, and The Broken Empire trilogy. Sadly, none of these are xianxia. Their types of "evil" differ: in Ouroboros Record, the MC isn't necessarily evil, but his goal requires him to do things that will label him as such. The same can be said about Dungeon Defense, though the MC in DD is a bit sadistic. As for The Broken Empire, the MC here wants to kill people on impulse and generally wants others to suffer, even towards his allies and those who wish to help him. Also, I remember there being a school arc in Ouroboros Record. It was pretty short, though
Oh, Spirit Vessel. Yeah, that one. The protagonist isn't "evil", but he is a chaotic neutral, emphasis on the chaotic. There also is a school/academy arc here that lasts for quite some time, though it happens after 100-200 (I don't remember much) chapters after the novel starts. And there's Divine Throne of Primordial Blood. The MC here, just like in Reverend Insanity, is one who likes to experiment. But unlike the one in RI, the MC in DToPB does experiments for a selfless cause of helping humanity as a whole. There's a school arc after the first few arcs.