Ok.
Firstly, sitting in detention for minor infractions is completely a waste of everyone's time. Agreed. So hopefully a sensible kid will not prat about in future, learn their lesson, & not waste their or my time with those 'minor infractions'. Honestly, I've yet to meet a teacher who enjoyed supervising behaviour detentions.
If you have several hundred people of whom some - usually a few- are constantly pissing everyone about, you do have to be seen to not tolerate it, or you end up with a lot more not unreasonably deciding that missing deadlines or whatever is ok.
Why wouldn't they? Getting the work in on time requires effort.
However, my lesson on Thursday is often about feeding back to the students re the piece of work they handed in on Monday, & I've been marking the blasted thing since then. If they haven't done it, it's a PITA for me, but more relevantly, they aren't getting that feedback.
So they need to sort it - independently is fine, if not, that is where detentions happen.
Revision sessions are an extra. I'm staying after school to help students who will benefit from that help. It's a privilege not a right.
If you miss my revision session because you're in detention for not having met requirements for another subject - well, that is how it's going to be.
Either you aren't really that bothered or you aren't coping with your GCSEs. Your results will obviously reflect this.
We can't just 'reschedule to the next detention slot'. Who is going to staff that one? We are all doing revision sessions every night.
Ultimately, don't get me wrong, I bend over backwards to help students! But if a student is unable to attend my revision session because they are behind in another subject then THAT is their priority. & if they are in detention for behaving badly - well, consequences are a thing. Their behaviour impacts on other students' learning.