Anything on the internet will eventually be turned into a childrens' chatroom.

Do you allow them acces to your school's website? Guess what's under one of these forgotten posts about a singing competition from 2012. Do you let them access some math exercise platform? Does it allow sending people invitations to work together and also let you set group names? That's a chatroom right there.

I think the coolest one I've heard about is prison tablets that didn't restrict access to WiFi settings, so people would set up personal hotspots and use access point SSIDs for communication between cells.