Thanks, everyone, lots of good feedback. My son is at a state primary school in Year 5. The school prides itself on its good sports results and the head of PE believes the good results justify the completely ruthless attitude to team selection. Personally, I think it's mainly an ego trip for her more than anything.
The school has received the sports mark, whatever that means, so I think they believe they are doing things right. Meanwhile, excellent players are losing confidence from being told they don't measure up, older/larger children in the year group are consistently favoured over smaller/younger ones, and players who are just keen to have a go won't take the risk of trying for fear of not measuring up.
We have an obesity crisis in this country, with our children lolling in front of screens all day instead of developing a love of exercise to take into their adult lives. Sport is a great opportunity to teach children that if they practice something they will improve, that it feels good to achieve that improvement, that hard work pays off, that teamwork brings success and that physical activity is fun. Teaching these important things only to the naturally gifted seems frankly stupid to me.
There are kids who love sport, and will make it a part of their lives right into adulthood. There are kids who hate sport and will not make it a part of their lives no matter what. Then there is the vast middle ground: kids who are keen but not terribly coordinated. Kids who like sports but not contact sports, kids who have some ability but are the only one of their friends who want to play sports. To my mind, this big middle chunk is where most resources should be allocated. They are the ones who could be nudged in the right direction with a little well crafted encouragement. And they are the ones being put off by the cut throat attitude.
For the record, the son in question is an excellent football player, so he is not even in the category I am talking about -- he plays in a competitive league on Sundays, a fun league on Saturdays, and believes that the only purpose of school holidays is footie camp. So opportunities to play are not the problem for him. His problem is that all his friends and teammates were chosen for the last match and he wasn't, causing him to feel humiliated and his friends to feel guilty. Not nice for any of them.
I've watched these kids play football for 6 years now, and to be honest there is not a great deal of difference in ability amongst the really keen ones, who number about half the boys in the year. Some are a bit better than others, but not markedly so, and really any random 11 would be about as good as any other 11, assuming you have a decent goalkeeper. So there is really very little purpose in only letting the biggest ones play for the school. All it does is put off both good players and children who aren't too great but should be encouraged to enjoy sport.
Sorry to go off on one there, but I feel sure there is a better, fairer, more educational and equally competitive way to run things.