Did you have to install an app called Company Portal or Intune? If no, then they probably don’t have access to your device, except for possibly being able to selectively wipe school data. They could also be using another MDM solution like Airwatch, but again, you would have had to have installed something (and unlikely, since universities get massive discounts on Microsoft licensing).

Even if you do have Company Portal, it doesn’t necessarily mean it’s managed as it’s still used to broker communication and authentication between Office apps on Android. The app itself would be able to tell you if the device is managed.

And as the other poster mentioned, if they had you install a root certificate for the university they can intercept and inspect HTTPS traffic from your device while on their network. But that still doesn’t give them access to the data-at-rest on your device.