This website http://0800reverse.co.uk/ explains how to make a reverse charge phone call. It could be a very useful thing for children to know if they run out of credit on their phone, or it gets lost or damaged. The class discussed it this morning and we even listened to a call. It costs £6 to accept the call (!) but we agreed that as an emergency measure it would be worth it.
Please find time to discuss this with them and…help them to learn your phone number off by heart!