Teachers currently start on £30k and move up the spine annually until they hit M6 which is £43,607. Seems fine. You can start teaching when you're in your early 20s and be on £43,607 by the time you hit 30. Unfortunately, there's no guarantee you'll move to the Upper Pay Scale (UPS) - that depends school policy. Similarly, even once on UPS there are different policies about how fast you can progress within that Upper Pay Scale, with many schools saying only moving up once every two years. Point being, not very many teachers are on UPS3.
I'm a secondary school teacher. The two best teachers I've ever known were both stuck at M6 (see above, school policy). Both of them had 20+ years experience. Both of them put in 60 hour weeks and worked through holidays. Both had training responsibilities for new teachers (which you don't get paid for). In other words, they earn a £couple above the minimum wage.
The problem is that we have a clause in our contracts that states 'and any other reasonable additional duties.' As another poster has mentioned, with the collapse of all other services, and the police taking a very hands off approach to any criminal offence committed on school property, these additional duties can get pretty wild.
You're stuck between a rock and a hard place. Either you let the kids go under, or you put in the hours.
And just for reference and regarding teaching support staff. Yes their pay is awful, but they do get to arrive later than teachers and leave at the end of the school day.