The 11+ was still a thing in South Wales in 1971. Everyone sat it as routine- it wasn't just children of the tiger mothers who could afford all the extra tuition. Kids who passed it went to grammar school, kids who didn't went to a "secondary modern" school. To give some indication of the spilt, in my area there was one grammar school and four secondary moderns.
Uniform policy was very strict, and still a bit Mallory Towers - we wore tunics with a blouse underneath, a tie, a beret and a mackintosh or duffel coat. We also wore dresses with navy knickers for PE, and all had to share a communal shower afterwards, naked.
The timetable was in four chunks of 2 x 40 min lessons. So two lessons/break/two lessons/lunch/two lessons/break/two lessons/home. As we got older, we used to have "double periods" (80 mins of the same lesson) and in 6th form we occasionally had a whole morning or afternoon of the same subject.
School finished at ten past four. Most of us walked to and from school, though there were school buses for kids from further out.
We also learned Latin from the first form up to starting our O Levels.