In a normal week (during normal times, obviously) I teach year 7 for 3 hours. It generally takes me about 20 minutes per y7 lesson to plan, because I've been teaching a while now, it used to take longer. I also mark their books once a week, which takes just over an hour. So that's about 2.5 hours of marking/planning. Multiply that by 5 for the main school classes I teach. I also teach 2 A Level classes, which are a relatively new syllabus (as in, I was on my first time through this new syllabus with year 13 when lockdown happened, I haven't taught it all yet). That's 5 hours of teaching A Level, but it takes me at least 5 hours to plan it currently because of the newness. And I have to mark their weekly homework too, which takes a good couple of hours per A Level class. So 5x2.5 = 12.5 for main school, 9 hours for sixth form. That's 21.5 hours of planning and marking. 3 of those happen during the school day (PPA time), the rest are before/after school. There are often extras to do as well, like year group meetings, department meetings, reports to write, mocks week (I could spend 6 hours marking one class set of mocks), parents evening, etc. I don't think I work as hard as some of my colleagues, but I would say I average out as working about 50-55 hours a week, as a secondary maths teacher with plenty of experience. I can cope with that, as I know there's always a holiday coming up, and I can mostly be home in time to collect my primary aged dd from childcare by 5ish (but I do then have to work later in the evening, that's the payoff).
I don't complain about my workload very often but I damn well will start moaning if other people start adding to it. I can do a good job at the moment by having very low housekeeping standards at home but I would do a significantly worse job if I have to have more pupil contact time. Every hour of extra face to face teaching would also require about half an hour of planning. When an I supposed to mark anything?