[mtmail]

Could you setup a local wifi network with monitoring, showing which URLs get accessed in real-time? These days connections are encrypted so you can only see domain names. Then explain that happens when they connect to any public wifi. How can you trust "<restaurant> free wifi" is really run by that restaurant and not the person at the next table?

> Find out their e-mail addresses (if publicly available)

That's probably against data protection rules set by the school.