And some people speculate my daughter may have logged into an account on my computer—there is no possible way, and at home she only uses one of two other devices (and at her school they don't have students log in off premises anyways), and my two computers are locked at all times when I'm not around.

In addition, assuming she were able to get access to one of my computers, the password manager is behind face/Touch ID and locks automatically after each use.

I spent a couple hours digging through all the emails we got from her school too, for the month preceding her entry into the school, and I saw nothing about any online logins, not even a link to any kind of portals or anything like that... just consent forms, welcome messages, and the like.

I've been racking my brain for a logical explanation as to why my personal email (and the password associated with my personal Microsoft account—which has been used to login to Azure in 2020, years before this mess) has been associated with the school's tenant. I can't find any.