Technically 14 - Was at a friends house and she had stolen some of her dad's beer - and she dared me to drink it - but there was a catch - I had to mix it with milk (was the only think in the refridgertor to drink) - let me tell you that was enough of an experience to put me off drinking for about 3 years. (I drank half of it and puked it all up within 5 mins ROFL)
Then I drank when I was 17. Not often cause my parents were pretty strict on me attending parties. Then drank a fair amount at 19-20yrs old - now I rarely drink. Maybe once every year and a half.
It's not a big deal if you don't drink but I can see how it can be seen as one, especially if all your friends drink and you are the "odd man out" so to speak. I wouldn't worry about it too much - there are probably a lot of other people in your school who don't drink or have never drank.
Anyway hopefully it helps knowing you're not alone!
Take Care