How can I disable menus ?

Hello ! 🙂

I’m a primary school teacher and I use WordPress Mu to create blogs for my pupils. We create blogs about specific topics (electricity, etc.) and some pupils have their own blog where they publish poetry, etc.
They are admins of their own blog. Anyway, I would like to disable some menus in the administration panel.

Can you tell me how I can achive this ?

Thank you ! 🙂