Sinsong - no you misunderstand me.
I'm saying, that in some places you would expect there to be supervision, because that's the done thing, (reasons are irrelevant) and if that expected/promised supervision wasn't provided then that is a problem. At no point have I said that they shouldn't supervise.
Other situation could exist where you do not expect supervision of the child, and if you're fully aware of that, you then decide if you're happy with the situation.
At no point did I ever imply that teacher's shouldn't be supervising the playground.
As for child protection, schools are taking an extreme line, because of child protection issues, which reach far beyond just the child. and is really not the topic at hand.
The topic at hand is how long should a child of 9 be unsupervised? You say never, unless they're in your house with you, others say it's fine for short periods of time in the right situation depending on the maturity of the child.
If you are really suggesting that you will continue to supervise your children until the day they turn 16 all the time they are out of the house, then... good luck with that! :)