The security of their personal devices on which they must install Microsoft spyware and accept it's terms, before being allowed to complete their education.
I'd say if the school isn't willing to modify their server configs to allow generic 2fa, they should be obligated to provide devices to run that app if they really insist on that app alone. Then maybe with that choice they might decide it makes more sense to reconsider simply having one admin do about an hour's research and setting some service options.