The term red-shirting around my area doesn't really have anything to do with kids close on the border or near the age level. It's used for kids who are far beyond the age level who have been held back, primarily for sports reasons. When you have a "5 by December 2nd cutoff" and kids with August birthdays who are 6 start kindergarten, that makes them sometimes 1 1/2years older than a chunk of the class.
I actually do fault parents sometimes- just being honest! If you need to hold your child back for emotional, social or academic reasons, I get that. However, in our area, the most common reason to hold a boy back is to force a situation where he is physically bigger than the rest of the group and therefore, a better football player. I wish I were kidding but I'm not. As a teacher, I've had 6th grade boys well into puberty because the family was raising a football player. Earlier puberty means likely making varsity as a freshman, regardless of actual skill.
