Benefits (athletic): player is better than he otherwise would be in that grade. That seems self-evident.
Risks (athletic): although the player is better than he otherwise would be in that grade, he's still not good enough to earn a scholly.
Here's an article from a few years ago. BTW, Mr Gerhart held all his kids back:
"Sociologists call it the relative age effect, or RAE.
It is a fancy way of saying that whenever children are grouped in one-year increments, those born immediately after the birthday cutoff can have mental and physical advantages compared to those born immediately before it. That the kid who is 11 years, 11 months old usually is a better pitcher in the under-12 league than the kid who just had his 11th birthday.
The older kid also gets the most playing time and often is selected to all-star or elite teams, where he is exposed to better coaching and a higher level of competition – which, of course, just makes him better. At a certain point, researchers suggest, it becomes a self-fulfilling prophesy.
Most RAE research has been conducted in Europe. One of the most extensive studies, published in 2005 in the Journal of Sports Science, compiled birth dates of 2,175 players (mostly boys) from youth national soccer teams of 10 European countries. The findings: 43.4 percent were born in the first three months after the Jan. 1 cutoff date, and only 9.3 percent in the year's final three months.
The RAE, the British and Belgian researchers wrote, “may result in significant differences in performance.” Numerous studies in the U.S. and elsewhere have reached similar conclusions.
And that's just for children who are six to 12 months older. Imagine the benefits of being 18 months older, or a full two years older.
Fifteen members of USC's 108-man football roster from last season, or 14 percent, are at least a year older than their natural class. At USA Basketball's Youth Development Festival in 2007, which gathered 30 of the nation's top boys high school players, 19 were a year (and in some cases two years) older than their typical classmates."