Aside from the fact that we don’t have spaces big enough for 60, and it’s very hard to teach 30 properly from the front, let alone 60, I don’t see how merged lessons would work in secondary. Maybe for Maths, where they’re all being taught the same subject at the same time (because of setting) but how does it work when one class is timetabled for Geography, another for French, another for Art...
When we merged classes before lockdown, it was just for babysitting.