Yes, I highly encourage you to join your high school junior varsity football team next season. Based on your height and weight, I believe that you will make a very good fit at defensive end. Considering your age, your size gives you the potential to become an elite high school defensive end.
My best advice for you is to work hard and perform very well in practice every day. In addition, what you need to do this (and every) offseason is eat healthy, exercise by doing weight lifting, and either jogging or going for a long run every day. If you do these things, you will get faster, stronger, and into better shape, which will greatly improve your chances of becoming a successful, top notch defensive end in high school football, who could go on to play college football in the future.