My kids have been to both public school and private school. We live in a fairly blue-collar community with a lot of recent immigrants, so in the public school there is some redshirting, but almost exclusively with boys with summer birthdays and not in the lower socio-economic groups. In the private schools, though, there is a ton of redshirting of both boys and girls with summer birthdays, including at least 5 boys in my DS's grade of 65 kids who have birthdays in March-April-May and pretty much every other boy with a summer birthday. The reported reasons are both academic and athletic. In fact, I've had one parent who redshirted her July-birthday daughter refer to a girl who was a year younger and not redshirted as being "young for grade." I'm not sure what that makes my two youngest kids, who were both skipped
Interestingly, quite a number of the kids who were redshirted actually socialize primarily with the kids a grade up, who are their age mates! On the other hand, they are also more frequently "moved up" to the higher-grade athletic team, (although that really just means that they are playing with their age mates). But it sounds more impressive to say that their child played hs ball while still in ms.
My neighbor actually brags to me that her 15yo son is accelerated one year in math. What that means, though, is that he, a 9th grader who is one month older than my son, is actually doing the same math as my son, who was not redshirted and so is in 10th grade.
As far as my kids go, the fact that they are in class with kids sometimes more than two years older than them means that they are with their academic (well, close enough) and social peers, so it saves them yet another skip. So far it has even worked out in sports (which are grade-based here). My kids aren't althetic stars nor would I call them natural athletes by any means, but they more than hold their own with their teammates because they play up to the level of coaching.
Of course there is always the dreaded driver's license issue. Some of my son's classmates were fully licenced drivers this spring and my son won't even start driver's ed until this fall (and this is my son who is in the correct grade for age, although the youngest in his class since he has a July birthday). Honestly, it hasn't been an issue at all.
