Play time: What if?
Fifteen minutes.
It's not long.
Factor in: getting coats on and off, eating your snack, getting out of the classroom, deciding what you're going to, who you're going to play with, what you're going to do and the umpteen other things that whistle through the head of the average primary school child, and is it any surprise that it looks like mayhem. And don't forget you're supposed to be going to the toilet now too. Is it any surprise that they come in from play all riled up about some seemingly innocuous incident that they didn't have time to resolve? Fifteen minutes and the bell rings signifying it's time to go in ...

Fifteen minutes. What could you get done in 15 minutes? Personally it's just about long enough to boil the kettle, sit down for a couple of minutes and 'enjoy' burning the roof of my mouth on scalding hot coffee.
But what if ...
What if play time was 30 minutes. What effect would that have on the well-being of the children in our schools?
When I'm doing what I do, the first time I say to the children, "Off you go and play" they charge around like lunatics. They can't decide what it is they actually want to do because there's so much potential. Fifteen minutes later, having weighed up all the options, they settle down: Some to play on their own, others to play together. They create and destroy worlds, both physical and imagined. They settle in to their play. But it's taken them 15 minutes.
The next time it only takes 10 minutes and by the time it gets to the third time, when they know that they've got 30 minutes of solid play, the switch into play mode, settled play mode, is almost instantaneous.
We do our children a massive disservice by limiting their opportunities to express themselves on their terms. We also make a rod for our own backs as we then have to try and rein in the madness while it's still at its peak.
From an entirely unscientific and anecdotal perspective, if we allow them greater amounts of time to play freely, I reckon we'd reap benefits in the classroom that none of us could ever predict.
There's a trophic cascade at work and play is an apex predator.