Tweaking from year to year really isn't the case, every child and every year group is different. Nevertheless, it is all the extras that take up the time, just planning and traching would be just about doable. Leading a subject (no extra pay), data collecting, inputting and analysing, marking, SEND MyPlans, Early Intervention Plans, Behaviour Plans, extra curricular 'voluntary' clubs after school, pupil progress reporting and monitoring, adapted materials for SEN/D children.
Also the meetings - termly meetings with all the MyPlan parents, parents evening, behaviour meetings, subject monitoring, cpd, safeguarding training, reporting and follow-up, ATS meetings, S&L meetings, social worker meetings...never ending!
Yesterday I was in school from 7:20 until 5:45, when the school closed. I did another hour in the evening and will then need to do a little over the weekend. In the holidays I always spend at least one day per week reviewing MyPlans, planning the next half term, timetabling etc.
Then there's the things TA's used to have time to help with, but now can't as they are so overloaded themselves with preparation and implementation of interventions and in class support for those with SEND. So printing, chopping up, photocopying, displays, laminating, certificates etc also all need to be done.
I actually do love it, I'm in the second ECT year and being with the children is amazing, but my pay is at the very lower end of your estimate and per hour is way less than I got previously as an HLTA because of the hours needed. Other, more experienced, teachers at my school work just as many hours, though obviously they do earn more.
It's a fantastic job and has been a really positive experience, but it is exhausting and takes over your life!