Without Annette by Jane B. Mason

Openly Straight and Honestly Ben by Bill Konigsburg

The Scholars and Sorcery series by Eleanor Beresford

As I Descended by Robin Talley

Girlhood by Cat Clarke

Bonus: Complementary and Acute by Ella Lyons is another one, separated out simply because it’s a novella under 50 pages

Double bonus: Little & Lion by Brandy Colbert isn’t set at boarding school, but does flash back to the bisexual MC’s relationship with her roommate there