User blog:Ameagle/Quick Question Regarding Cover Letters

I'm currently a senior in high school and I'm working on a new short story to submit to the Virginia Woolf Short Fiction Contest hosted by LitMag. I'm not necessarily close to finishing, but hey, I'm making progress and I still have like 56 hours left, so, whatever.

However, I have been looking at the registration process, and it looks like they're asking for a cover letter as well. This is my problem. My short story Charlie has been publsihed in a national magazine for teen writers, but besides that, I have no real writing credits. So there's not much else that I would have to mention in a cover letter besides my (future) high school diploma and my semester I spent interning for my school's creative writing class.

How would one of you go about wording a cover letter in my situation? Should I mention the fact that I'm still in high school? I realize the idea of a high-schooler winning a national writing contest for big kids is kind of silly, but I'm going to be an adult next year, and I just want to see what I'm capable of.