Curious- and wondering whether it'd considered a good idea for 'school unity' or cohesion if schools DID have such a space these days?
DS1 secondary (Y7-11) has a hall but it's a proper, professional theatre with fixed, raked seating which will sit 450, but the school's 1450 strong- each year group is 280, so no chance!
Another local secondary here has House assembly so can get a third of the school in at once which I guess is a good compromise.
My school had a typical 'assembly hall' into which all 1100 (Y7-13) of us could fit but usually every day, one year group of 120 had their assembly in the old small school hall (and thh Sixth form could choose whether to go to assembly at all) BUT it was possible to get the whole school into the big hall.