What do you call the university or school people graduated from in one word or phrase?

The alumni of a school, college, or university are the people who used to be students there.

But what do you call the university or school one person graduated from in one word or one phrase?

Good old FU. That's my

alma mater

al·ma ma·ter
älmə ˈmädər
noun

the school, college, or university that one once attended. the anthem of a school, college, or university.

Source: Google

It sounds funny because it's a Latin phrase. The words literally mean:

alma, "nourishing/kind"

mater, "mother"

Source: Wikipedia

But few English speakers think about that when referring to a school. It's the kind of thing only us word nerds care about.

In British English, you'd probably just say that the university in question was your university or your old university

e.g.

My university was very nice

My old university was Oxford Brookes.

etc.