Here in The Netherlands, my oldest daughter (12 years old) had her class as her normal schedule between 5 and 8 hours per day. It was too much for her at some point. She got a lot of headaches during that time. When she was off the screen, the headaches were gone most of it.
The last two weeks before the Summer break, she was going in small groups. Only the teacher was allowed to open Teams and add the other classmates in a virtual class.
She was glad that she could go back to school again. They did not with the screen, but with books. The other half were on screen. The other day she was on screen and the other group was in class.
I hope this all will work out for the kids.