Ouch Traci, it's a tough age!
Tell your son "it's her loss" and theres LOTS of other girls waiting inline for him to ask them out.
On second thought, please tell him to ENJOY his young life, and theres plenty of time still for him to date girls!
My son dated a girl for 9 months, it was a total nightmare, she had some baggage with her while she is a year younger then him, and he was so not ready for all that.
I now encourage him to stay single, stay young, and ENJOY life with his friends.