Just re-read the link, and the head's comments that a playground for that number of pupils would have to be 'huge' and the situation, or the pupils, would therefore be uncontrollable.
It doesn't have to be like that. The 1700 pupils at our school aren't milling round one huge area.
There's a playground purely for Year 7s, to help the settling in process and so they don't have to turn up on day one and be faced with loads of older, bigger pupils.
Year 7s don't have to use that playground though, to my knowledge my children never did, but it's a safe, unthreatening space for them if they want it.
There's a playground for years 8-9, and I presume there's one for the upper school, although my children haven't quite reached that stage.
There's a large field which pupils can use except in wet weather. There are also various small areas pupils can gather in. My daughter and her friends tend to congregate in 'the Japanese garden', a really nice little area with various types of seating and attractive planting. That's where they hang out, gossip and eat their lunch in all but the coldest weather.
Children need breaks - don't we all? It's not just the running around, many children choose not to do that. It's the getting together with your friends, some of whom may not even be in many of your classes. It's about having some breathing space and some unsupervised time.
The idea of children being escorted to the dining room for the lunch and seemingly supervised during just about every minute of the day chills me. I don't know any work environment that operates in that way either.