The answer is do it later. Wait for college. Going to a college like USC or UCLA is a safer way to make the leap. These universities will help you get training and experience as well as make connections to jobs. Plus it gives you a safe place to live while you develop your LA network (and having a network is very important to be successful). A network consist of people you know in Hollywood that can help you get jobs. Without a network, it is very difficult to get an acting job.
But a lot of young actors don't want to wait. What can you do before college? Here are some ideas:
1. School plays are great experience. Casting directors like actors with theatre/stage experience.
2. Community theatre plays are another way to train yourself and work with adult actors who can teach you a lot and maybe even help make connections.
3. Make your own short films. Even if you make bad short films, you still learn a lot of acting and then watching yourself. Have fun with it and don't worry about being good. But watch the finished film and think about how you can do better.
4. Start a YouTube channel. You can even make a little money by monetizing the video. And if you're lucky, you'll have a viral hit and make your mark early.
Trouble with Convincing Parents
If you're having trouble convincing your parents, doing the above 4 steps will show them you are passionate about being an actor and they will be more likely to support you if you show your love what you're doing.
More acting tips at http://www.freedrama.net/acting.html