It's nothing to do with its membership figures, which remain healthy, or its relationship with ministers, which is still cosy. It is about fishing.
The latest edition of the union's magazine Teaching Today reports on its last annual fishing championship, held on the Warwickshire Avon.
"Torrential rain caused the river to colour up and rise two feet," it said.
"Catches were very disappointing and the winning weights were the lowest since the competition started in 1995."
This will not do. We hope to see general secretary Chris Keates there this year with dynamite and a very big net.