i would like to add on to this, do not bring your own device, just simply keep school/work and personal stuff entirely separate. simple as that.
all work and schools that allow you to use a personal device that I'm aware of will require you to have whatever software for surveillance that they have on provisioned devices, you'll likely end up messing up and leaking something private, and it just takes up storage space.
it's the organization's device, they can put whatever nonsense they want on it, just be sure that you only ever use accounts from them on the device. never a personal account of any kind.
telegram isn't even e2ee, why would anyone recommend it.