My children attend Catholic school. The middle school kids at the school range in age from 11 to 14. Some of the 14 year olds "date," but that means their parents allow them to take the guy (or girl) to the movies with their entire family. I used to "date" at age 12 (6th grade). That meant my so called boyfriend walked me and my books home, met my mother and we played kickball outside w/ the other kids in the neighborhood. It also meant we danced almost every dance together at the school prom.
"DATING" can mean many things. If it's more than what I mentioned above, than I believe that 15 IS TOO YOUNG TO DATE. But if it's as innocent as what I mentioned, than I think it's perfectly OK to "date." Parents need to use their best and most cautious judgment when it comes to this issue!