My University had GSuite for all students and faculty. Meet supports up to 250 participants for a normal call and Livestream only for up to 100,000 viewers.

I imagine Microsoft has a similar offering for schools that use their products. I don't see a case where it makes sense for schools to be rolling their own livestream platform and paying these fees.

Edit: I'm not positive if the Livestream capabilities are included in the free Education package or just the enterprise package.