That's something we do do on request, because of precisely that problem. Of course, it also blocks staff from editing. It's a pity we don't have an automatic time-of-day blocking mechanism, that hits only class time ...

Best thing: get your IT person or an organisational higher-up to email me (dgerard@gmail.com) asking for such a block on a given school IP, and I'll say on the user page for the blocked IP that they asked.

Second best thing: find such a person (usually the IT person) who will act as a first contact in case of such vandalism who is able to deal swiftly with kids being stupid on the wiki, so they can be contacted by an admin who would otherwise block editing, and can find the kid and have a Little Word with them.

The usual mechanism is to block anonymous editing, with this as the blocking message.