Here are some tips for talking to you parents about choosing veg.
Put yourself in parent’s shoes. Your parents care a lot about you, even though it might not seem like it all the time. They only oppose your new diet because they think it will harm you in some way–they think you’ll be unhealthy or deprived if you change your diet. Or, they just don’t know how to help you become vegetarian or vegan, or they don’t understand why you want to vegetarian or vegan. They want the best for you, and you need to show them that vegetarianism is best for you.
Be firm about your new choices and be persistent. Be confident that all of your parent’s fears about vegetarianism or veganism are myths.