I stopped DS working at 8-something tonight, after he'd been working for 12 hours with only short breaks. He started school at 8 this morning, an hour for lunch, a compulsory revision session after school, and then when he got home, he started immediately on the homework that he got today, that's due tomorrow. He had a short break for dinner and, when I went up to his bedroom just after 8, he'd just finished the homework and was about to start revising.
So, the school made a 12 hour day mandatory, and expect revision on top.
If this keeps up, DH or I will intervene and address it with the school. I can hardly believe that this is what the school intended.