is it legal to hold students after school for an hour every day

I have my GCSE exam in a couple of weeks. The problem i am facing now is that I have to stay after school every day depending on the exam I have. Usually, I have to stay after school 2 times a week(which I hate ).
The problem with staying after school is that it does not benefit me as i am just taking notes and, I have my notes ready i just have to learn it and do practice papers. I tried to discuss this with the teacher in charge of period 6 but no one is listening to me. is there anything i can do
(note: usually in my period 6 class, I am in a subject that i already have a high grade for and the subject that I need I am not being placed in it)

Well, they's quite a lot to unpick here.

First you say "I have to stay after school every day" but then say, "I have to stay after school 2 times a week". Those are quite different. Which is accurate?

Then you talk about Period 6, which sounds (from its name) like a normal part of the timetabled day. Is Period 6 the name of the "after school" time you refer to? If not, why is Period 6 relevant to the question?

You say, "usually in my period 6 class, I am in a subject that i already have a high grade for and the subject that I need I am not being placed in it". That makes it sounds like Period 6 is a subject-specific "revision" session, or similar. Is that what it is? You'd be happy to use Period 6 to revise subject A, but they're making you revise subject B - which you "already have a high grade for". Have I got that right?

What's stopping you bringing in your notes, and learning them / doing practice papers? What about Period 6 means that only thing that you can do is "just taking notes"? Is it because there's actual teaching going on? So it's not a subject-specific revision session?

Well, they's quite a lot to unpick here.

First you say "I have to stay after school every day" but then say, "I have to stay after school 2 times a week". Those are quite different. Which is accurate?

Then you talk about Period 6, which sounds (from its name) like a normal part of the timetabled day. Is Period 6 the name of the "after school" time you refer to? If not, why is Period 6 relevant to the question?

You say, "usually in my period 6 class, I am in a subject that i already have a high grade for and the subject that I need I am not being placed in it". That makes it sounds like Period 6 is a subject-specific "revision" session, or similar. Is that what it is? You'd be happy to use Period 6 to revise subject A, but they're making you revise subject B - which you "already have a high grade for". Have I got that right?

What's stopping you bringing in your notes, and learning them / doing practice papers? What about Period 6 means that only thing that you can do is "just taking notes"? Is it because there's actual teaching going on? So it's not a subject-specific revision session?