What math class are you in now, and what classes do you plan to take later in high school and college?
Are you nervous for a good reason (such as you're not doing well in your present class), or are you just nervous? If you're not currently doing as well as you would like, it's possible that you don't know the material in previous classes as well as you should. If that's the case, set aside some time regularly to go back and review the material you're weak on and work problems in that material. One of the best things you can do to instill confidence is to increase your competence.
just realize math is like any other skill - it takes some practice to get good at. Don't get fooled by those "smart" kids, chances are they just practiced and did their homework. Very few people are truly gifted at math, but anyone can be good at it.
I love math! I dont see why you should be at all nervous or scared of it. Believe me, I used to suck at math! It was horrible, but then I started getting the hang of it and started excelling in it. Just got to practice and dont get scared when you see a problem, equation, or formula. :)
Like the other people said, the more you practice, the better off you will be. I used to hate mathematics, up until last year. I think the reason was that I never felt very uncomfortable on the tests. I would try to study my notes instead of doing the assigned problems for the exams. Although this tactic worked in my other courses, math is different. The more problems you do, the more comfortable you will get. Good luck!