If there are any antis in your school, they'll probably put up posters about the annual "Meat-Out". Put up some anti-anti posters to counter them--you can find things like that on web.

Also, writing your elected officials isn't a bad idea. I got in politics pretty heavily when I was around your age, and I used to fire letter after letter to politicians. You might not be able to vote quite yet, but you will in a few years, and politicians want all the votes they can get.