Age Differences and Teen Dating

My son is 15 and pretty cute (if I do say so myself) in a Harry Potter kind of way. Recently, our little girl neighbor started following him around, and we started kidding him about his new girlfriend, thinking she was just 10 years old. He met up with her yesterday and they talked. Apparently she is 13, not 10, and wants to "date."

We stopped kidding after that. I wasn't sure how I felt about the 15/13 dating scene. It sure didn't seem very funny.

We started dealing with dating a couple of years ago, when my son was himself 13. The other kids were "going out" with each other, though that basically meant giggling across the yard from each other at lunch. Back then, we came up with a set of rules that we've stuck to: Our kids have to 1) be at the same school (which rules out a middle school/high school thing or high school/college thing) and 2) have to be no more than one grade apart. There just seems to be such a difference from year to year with teenagers. Kids change (and mature) so much during ninth grade. I just don't think middle school kids are ready to be "dating" high school kids. But in this case, they are at the same school. They're just two years apart, and holding to that rule is harder.

A friend of mine said I should tell my son that he would get in a lot of trouble with his friends if he started dating someone that much younger. Maybe my opinion doesn't matter, but the opinions of his friends could mean a lot. I'm going to try that ... and anything else I can think of to convince him to "let her down easy." I just don't think this relationship should go any further.