I teach 15 classes and I have to mark their books + homework once every three weeks inc stickers showing progress etc etc. That works out at a set of books and a class set of homework per night (5hours) plus planning and paperwork at the weekend.
That is impossible for me to do with my fatigue and depression, to be honest I don't think anyone can do it long term. It is terrible for my mental health.
Yes Union are involved.