@doschicos I would say approx 15% for boys, 5% for girls. And the 50/50 split for sports matches my experience. Again, in this case, we’re looking at a sample size of 1. 
Also, the concept of redshirting freshman is not exactly new. The below article is from 2005.
http://www.nytimes.com/2005/11/06/us/education/if-at-first-you-dont-succeed-enough.html