That's something I've learned today - didn't realise that railcards provide discount on 1st class as well as standard class.
Some do, some don't.
All ticket types: Disabled, HM Forces, Senior, Two Together, Veterans.
All Std Class plus 1st Class Advances: 16-25, 26-30.
All Std Class only: 16-17 Saver, Family & Friends.
Std Class only, excluding Advances: Network, Jobcentre Plus.
All regional railcards, such as Dales and Devon & Cornwall, are Standard Class, excluding Advance, only.
E&OE