I had a friend in high school who wanted to join, but couldn't. She kept going to church with her parents and also came to the LDS church with friends and would always come to our youth activities too. Her parents made friends with some other parents and talked to the missionaries to understand more about her desire. She had to wait until she was 18, but her parents were okay with it overall because everything was open and honest. Good luck talking to your parents! Keep praying for help & Heavenly Father will help you all along the way! Ask the missionaries for a priesthood blessing too.