I don't think we have much redshirting around here, but there was no way we would even have put DS in the class he should have been in, much less the one after that. His birthday is six days past the cutoff, so the year he turned six he should have just started Kindergarten, but he skipped that and went into first grade. If we had had any reason to consider redshirting, that would have put him in Kindergarten at seven instead of first grade at six, which would have been insane. He's never been a sporty kid, though, so academics were our only concern.
With another grade skip under his belt, now he's going into 7th grade at ten, turning 11. He's taking up cross-country and track, but size isn't too much of a concern there, so it still works out.
But he would never have been the size of his classmates even if he hadn't skipped, so there is nothing we could have done even if we'd wanted to.
I love the ideas mentioned above, in countries that run sports by age -- the only improvement there would be to run sports by size! Of course, if a small kid had his heart set on football and had to wait years to be big enough for it, that might not be good.
