We got our son involved in serious T&F at what some considered late, the tender age of 11. While playing Football, Wrestling and Baseball, I actually took my daughter to an AAU track practice, we found out it wasn't in her to run although she had a lot of potential. That being said, I came home and discussed with my son the thought of mixing in a little track during baseball season with the thought of it helping him in Football. To make a long story short, he began to run serious AAU T&F and within 2 years he was in Des Moines, Iowa and running in the AAU JR. Olympic finals of the 100 meters. He finished 6th in the country! I wished he would have kept running almost instead of playing football.
Anyway, my advice to you is, if you want to see how your kids stack up against the competition and improve and or try to get a track scholarship, I would find a local AAU Track Team and join them and work out with them. Generally, there are good coaches out there. Now AAU T&F is mostly made up of black athletes as I have said before, most white athletes are playing baseball, but that never bothered me and I consider one of my sons black coaches to be a big part of how he got to the Junior Olympics. He was very helpful with my son, even when he started to out run his own son, who was a defending state champion. I'm sure there are some AAU Teams in your area. I remember some good athletes making it to the Nationals from Georgia. If you want to compare your sons times to the AAU. Go to the AAU T&F site and Junior Olympics. It will give the times of some of the best runners in the country in each age group.
On a side note, running track actually helped my son get looks from historically black colleges to play baseball. I guess there's not enough black baseball players to fill their rosters? He could have played baseball for free at NC A&T, because a black track coach told the baseball coach about my sons speed and that he played travel baseball. Go figure?
I hope this helps. If you have any other questions DD, let me know.
I looked up the top 40 in the 13 year old 1500 meters at the AAU Nationals. It looks like the top 40 run between 4:18-4:59. Not sure how the 1500 stacks up to the mile. But that gives you some idea of the competition. ...and I saw some kids running from Atlanta, Lawrenceville, and Sugar Hill Georgia, if that helps.
BTW, I saw the AAU National CC event in Knoxville TN. Did your son run in that event?