To the OP asking what I do in my unapid work time:
1 have 4 60min periods free per week - the minimum you can get. One of those is allocated to phoning parents and do admin around my tutor group - typically, chasing reports, sorting out physical fights, chasing truanting students and issues students have in particular lessons, then reporting on the system and back to the Head of Year.
So that leaves 3 hours a week. They're mostly taken up with photocopying, liaising with other staff to swap rooms (for specialist teaching), tidying my room (because kids typically like to throw anything from pens to homework projects across the room - yes I report it and no, it doesn't get dealt with by senior staff) and printing paperwork necessary to evidence that I'm doing my job.
I teach, on average, 27 students in each class, of which I have 7. Each set of class books takes 2 hours to mark according to our guidelines with 4 stamps and for every lesson, plus hand-written comments and updated trackers. That's 14 hours spread over 1 1/2 weeks - the minimum. Then I marked and tracked 4 sets of tests this week - about 1 hour 15min each.
I also teach up to 6 lessons a day. Each of which can take anything between 5 and 30min to plan and resource (I have about 15 years experience, so some lessons do take little planning). Then I need to photocopy said resources. On average, the copier jams once a day. Which needs sorting. Usually by me.
This week, I had to check the marking of every set in a year group - 8 sets today alone. I had 20min allocated for this. Taking the required pictures, writing and processing the forms for this took an hour, because I am a fast worker. One set showed issues - I now have to follow this up with the teacher and then check again. In my own time.
I also wrote 30 reports and had a parents evening lasting until 7.30pm (no time to go home), in addition to 2x30min revision for year 11. None of this is paid, but all of this is normal and expected.