Have you noticed?
In the context of overall rising standards, it is difficult to determine whether boys are actually falling back. Could it not be that girls are merely taking their rightful place? As a parent and childminder, I know that little girls generally develop intellectually and socially much more quickly than boys.
They learn to talk sooner, take responsibility for their own feeding, dressing and toileting earlier, rule the household with a rod of iron by the time they are three, and at six are ready to govern a small country. Of course their A-level results are better.
Our local senior school still has a "Girls Room" where the delicate little flowers can retreat from male rough and tumble at breaks and lunchtimes. Most girls resolutely ignore it and congregate, as they always have, in the loos. Those who still use it remind one of tales in the Sixties of Japanese soldiers on isolated Pacific islands still resolutely fighting the Second World War.
It is safe to come out now ladies. We won.