Looks like GNE are backtracking on now allowing Student ID cards as proof of ID.
Still surprised they didn't allow this from the start
We’re pleased to announce that working with local colleges we’re near to agreeing a standard for accepting their ID cards for young persons' fares. Existing arrangements remain in place for now but we hope to have this launched in the next few days. Please check back for updates.https://twitter.com/gonortheast/status/1179388076080148481