If you'd take one where they do go to school but the school is certainly not the point, and the kisses are freaking awesome, I'd recommend Obsessed.
https://kisskh.at/22646-history-obsessed
But if that's not ok, then the history series has another one with good kisses and no school, and that's Trapped.
https://kisskh.at/30567-history3-trap
...Aaaand this is the moment when I realize how many freaking BL series are set in a school. o.O