I would avoid it until you are older. Your body is still growing and developing at this age and it is very, very hard to replace the goodness of meat with supplements and vegetables. I was vegetarian for a year when I was your age, and even though I did everything the doctor suggested (that's another thing - you absolutely must contact a health care professional), I was weak, underweight, I had no energy and just before I decided it wasn't worth it I fainted twice. And I was doing everything by the book. 5 years later, my iron levels are still too low. That could just be me, but my 12 month vegetarian stint certainly didn't help. There are better ways to make clear your opinions on animal rights, such as petitioning and limiting your intake to the minimum recommended level if you insist. Cutting out meat entirely will only cause you problems. Also, one person not eating meat is not going to stop people eating meat globally. We have evolved to be omnivores - it's what we do. The way we slaughter livestock is completely humane 99.99% of the time, despite what sensationalist websites will tell you. Seriously, there are better ways to fight for animal rights.
Personal experience. Go talk to a doctor for dietary info, go to a library for reliable and relatively unbiased literature (_Not_ the internet :P)