A lot of folks talking about the awkwardness or social stigma of being held back a year and yes, if your kid is in 7th Grade of your local K-12 public school system, and you are able to have him/her held back a year, for whatever reason, there will be an awkwardness. It will be glaring. Obviously, holding the kid back for Kindergarten if you are that forward thinking and the thought of spending $ on another year of day care is not a hindrance might be easy to do, but man that's a lot of forethought.
Since it's March and Madness is in the air, click on any D1 basketball roster , and see how many players were recruited from private schools (especially rosters from schools say, east of the Mississippi River). If you really study it you'll see many of the same prep schools popping up year after year on top contending teams. Prep schools like Oak Hill, Brewster Academy, Blue Ridge, Word of God, Northfield Mount Herman, Montrose Prep, Voyageur, New Hampton, IMG, etc. I'd be willing to bet that 90% of those players attending these type of schools transferred there after their Jr. year of public HS, then repeated Jr. year again, thus dropping down a grade and "reclassing" as it is called.
As has been mentioned here already, my understanding is that Florida has restrictions on this (reclassing), as in you can't do it in Florida preps like Montverde and Bolles. And most Catholic HS across the nation don't allow it. So your powerhouse Mater Dei (CA) and DeMatha (MD) basketball kids should be true to their year.
Probably more common in the basketball world as the body type is a completely different one than the baseball one. We're talking probably a stereotypical 16yo college hoops prospect of 6-6 and 165, versus a 16yo baseball prospect of 6-0 and 185lbs . You tell me, which body type would benefit most from an 5th year of physical maturity and development in the HS years in order to physically compete with 22-23yo men?
Click on the CWS rosters in June, and you will not see the northeastern prep schools on there. You will almost exclusively see public HS, Catholic HS, and a few private day schools. A much different HS journey than the D1 basketball player. And much of it due to the quest for that 5th year of HS development. Basketball prospects need it much more than baseball college prospects. It's just the nature of the beast.
The "reclassing" move is standard fair in the college basketball recruiting world. Not even a thought. Almost assumed. Even encouraged. Not seen as awkward, or embarrassing, or anything like that. Now, in baseball? No, not the norm. That 90% quoted above turns to maybe 5%. As a matter of fact, re: MLB draft, the trend of late is one of youth. The 17yo SS stud is more coveted than the 19yo SS stud (all things being equal).
So many variables, each kid and family, so different. Just do your homework, and try to do what's best for your kid. In regards to "gaming the system" in taking that extra year, I disagree. In college basketball recruiting, it IS the system.