People in from before 7am, on call 24/7 as DSL, providing cover during PPA, on playground, lunch, break and after school duty, open evenings, open mornings, admissions meetings, dealing with the LA, the Virtual School, the DfE, ESFA, IT problems, setting up student accounts, maintaining staff accounts, governors' meetings, data drops, departmental meetings, safeguarding training, strategic planning, intervention classes, reports and assessments and marking, pastoral care, behaviour management - somebody might get ten minutes here and there if they lock themselves in a cupboard, but usually, there is always somebody, staff or student wanting a piece of them.
A realistic day is for a late start at 7.30am, then briefing, then playground, then register, then assembly, then lessons, then break, then lessons, then lunch, then lessons and perhaps a PPA where you have to break up a fight in the corridor, then register, then playground/bus duty, then meetings/trainings/twilight/detentions/calls home/meetings, out nice and early by 5.30pm because the site manager needs to lock up. Nice, easy ten hour day, maybe nine hours fifty if the locking oneself in the cupboard worked. Smidge under 49 hours. Add in Saturdays, holidays, trips and events and you're looking nearer 10h x 195 if not more, giving an hourly rate nearer the £20 an hour mark and significantly less for many.
And support staff get even less.