OK, I'm in an independent school, Physics, year 9 to 13, each differs, but probably looks different to state colleagues.
My day starts at 7.45 and never ends before 6 on a weekday, Saturday varies depending on fixtures.
7.45 Breakfast
8.15 staff meeting
8.45 registration
9.00 assembly
9.10 until 11.00 teaching or on a free
11.00 until 11.20 break (often on duty)
11.20 until 13.00 teaching or on free
13.00 until 14.20 lunch (often on duty or running a lunch club)
14.20 until 15.00 teaching or on a free
15.00 until 15.20 afternoon break (never on duty)
15.20 until 16.50 teaching or on a free
15.50 until 17.00 collection or boarders tea
17.00 until 18.00 prep
twice a week I then do...
18.00 until 18.30 dinner
18.30 until 22.00 boarders free time (supervising or drinking tea or both!!)
22.00 until 23.00 late duty (sat in the house office chatting to the matrons)
Marking generally is done on a Sunday, 4 to 6 hours normally
First two weeks of most holidays we run 9 til 5 holiday clubs.
Admin is very limited, we do a three hour safeguarding course annually and a day of first aid.
The school doesn't require lesson plans, so each department has a broad scheme of work and you take it from there, some staff like individual lesson plans, fair play, I use a card index card with the key points I want to hit, we don't have to do WALT/WILF and all that jazz (or whatever the current version is)
We get OFSTED for boarding only, the rest is inspected by ISI, 22 years and I've had 2 in house observations lasting less than 10 mins each and one ISI chap who came in and had a good chat with me about rugby (which I don't teach)
In that regard, although a very busy job, there is no stress and the admin is probably at the level a state sector teacher experienced in the 1960s.
Worth re-iterating all Indies are not made the same.