Is it permissible for a principal to make his teachers come on Chol Hamo’ed Sukkos?
If it is a davar ha’aveid, meaning that the school would otherwise incur a loss, it would be permitted to do so. If at all possible, however, calling in teachers on chol hamo’ed should be avoided. For Torah study, however, it is permitted.
Sources: Shulchan Aruch 545; halichos bas yisrael in the name of Rav Moshe Feinstein.