My son goes to a school where the boys transfer to "senior school" at 13+. Theoretically. (They turn 14 in their first year of secondary school.)
Some parents transfer their boys to schools at 11+ (they turn 12 in the first year of secondary school), especially when they wish to opt out of the independent system back into the state grammar school system.
Also, the "Common Entrance Exam" at 11+ is much less stressful than the one at 13+ as the children only do three papers (I think) as against five or even seven (or something like that) at 13+.
Because I used to hang about the school premises a lot, I hear a lot of what other teachers and parents have to say. This was the real bonus of running the PTA back then.
I was convinced that transferring at 13+ was more beneficial to my son than at 11+.
First, boys would have some experience of leadership at this school before transferring.
At 13+ most of the boys would have had a chance to become a prefect, a monitor, house captain and vice-captain, or a wide array of other responsibilities (librarian, music monitor, games monitor, lunch-time monitor, etc).
They would have had several years of taking part in the House "hustings", at both asking questions at the hustings as well as standing up to say why someone should vote for them.
When they transfer to secondary school, although they lose their senior status to become the most junior at school, at least they have had a chance to learn to stand up for what they believe in.
Boys transferring at 11+ simply move to another school and often have to wait several years when they get nearer the top of the school to even get a whiff of leadership opportunities.
Most significant of all is the fact that 11+ boys are often pre-pubescent. They are often physically small. When they transfer to a school with girls at the same age who are much bigger than they are, it takes quite a bit to adjust to.
Even if they went to an all-boys school they run a higher risk of being bullied due to their being so small and young.
If the school has an ethos of supporting and mentoring the youngest boys - as some do - then they might have a great time. If the school has a culture of bullying, especially if schools are very large, then the new boys need to find protectors.
Sometimes these "protectors" are predators, members of gangs outside the school, as well as in the schools.
13+ boys often already have their voices broken, or they would have bulked out in readiness for growth spurts. Emotionally, too, they are going into a different stage of their development.
The teachers in my son's school tell me how nice it is to have the boys for an additional two years. They can see them maturing - OK, some get really annoyingly moody - but they feel that the boys gain so much confidence that they are more ready to take on the new challenges thrown at them at senior school.
At 11+ my son is still going through what I call "the silly stage".
On one hand he's trying to grapple with simultaneous equations. On the other he still chuckles with wild abandon at Spongbob Squarepants.
Some days he is very grown up, and we discuss some very serious societal matters. Most days however his mind is pre-occupied with the games he gets to play on the computer.
It has long been acknowledged that boys and girls mature at quite different speeds. I find it very difficult to understand that this in not considered when designing school systems.
Here in my London borough schools used to transfer children at 12+, an anomaly as far as the rest of the state schools are concerned.
They "corrected" this anomaly by lowering the age at which all children transfer. Just so that it would fit better around the national testing regime (called 'SATS' which I think stands for Standard Assessment Tests).
The bureaucrats overlooked completely the natural physical and emotional development of the the children. Instead they adjusted the school system so that the children could fit around a man-made bureaucracy.
Looking at the PSLE in Singapore I wonder how many boys would do much better if they took a streaming exam at 13+ instead of 12+ as they do now.
Of course there will be boys who would do extremely well even at 12+ or even 11+. These are the boys who have been drilled and trained into doing hard work by their parents: Does not matter if you are not naturally gifted in piano-playing, you will practise an hour every day and two hours for the four weeks before an exam.
Boys (and girls) who, for whatever reason, have been trained to practise will do well in exams, whatever age they sit for them.
But would a larger proportion of boys be streamed more accurately if the exam took place just one year later? When their emotions are more in sync with their growing bodies?
I don't know. But I think a later exam age would be advantageous to boys who are gifted but somewhat lazy, a bit like my own boy.