I can tell you about one outstanding secondary comprehensive school. However I have no idea what other schools do, except that this school tends to do whatever is considered best practice so other schools probably do something similar.
Ds1 is going into year 9 this week. He was top set all the way through primary school, and never really challenged.
Primary school tended to aim for 2 sublevels of progress per year, but they were happy enough with 1.5 and would even accept 1 (plateauing). Whereas, secondary school looks for 3 sublevels.
This was great for DS1 in year 7. In maths, he was a 6 in year 6, but in year 7, his target was 7a. The pupils were split into sets and the work was definitely more challenging than primary school. He got the 7a.
The following year, Y8, the target was 8b. He got 8a after 4 months. However, now some of the top set students were labouring away still stuck on level 7, so it became a mixed ability class once again, just like at primary school. DS1 was bored and unchallenged for most of the year.
It was as if someone had opened the valve just a little bit wider, he'd responded to the challenge and now he had to learn to wait for the others to catch up again (just like primary school).
The head of department and the teachers spoke of differentiation within the top set, but, just like primary school, it wasn't really differentiated work: just more of the same offered in a slightly more complex way. So, DS1's experience was more or less the same as it had been in primary
Science, English, MFL and PE were also set by year 8, and it was the same story there as in maths.
At Ds1's school the top set get less homework than the lower sets - actually they get none. However, I hear parents of children in the lower sets talk of three hours per night. I suspect that the explanation is that each set gets taught the same things at the same time with some classwork and some homework. However, the top set do their homework in the lesson. This enables the school to move children between sets without the need for catching up.
The big difference at secondary are the school clubs. They are like a visit to the science museum, and the only place where DS1 can access something new. That worked well in year 7, but by year 8, the need to avoid being labelled a "geek" got in the way.