You should look at the wider picture - what's good for the average child? Is 90 min enough? That's the question.
If a child isn't great academically, why can't they shift focus to a sporting career? Surely we should allow individuals to pick a schedule that suits their needs rather than imposing this belief that studies should always come first.
In principle, yes. But the problem with sport as a career is the same as acting as a career. It's fantastic for the tiny proportion who become world class and reach the top. But for everyone else it's a miserable career. Don't put your daughter on the stage Mr Mack.
So yes, in principle, if a child is no good at academia and great at sport, why not follow sport. That would be good for rooney junior fifteen years ago. But Rooney junior had fifteen mates who were also little buggers to teach. Let them do sport too and fifteen years later what have you got? Fifteen young men in Liverpool with no employment skills.