Tell them that they are going to have to trust you. Tell them that sport don't make people do drugs, people just decide to do them or not. If you wanted to drugs, you'd already be doing it regardless if you were skateboarding. No one wants to become a skater just to do drugs. You pick up skating because it's a lifestyle and an incredibly fun sport. Most skaters don't do drugs because they believe it hinders their skating.
Parents are always afraid of the child's accident during skateboarding. Hence, convince your parents about skateboarding with the rules and regulation so that parents will enjoy seeing you your skateboarding passion.
Honestly, skateboarders doing drugs and all that is a stereotype. Tell them that. Say, "I don't ever want to do drugs, I know tons of skaters who are very nice people but still skate"
This is the problem with parents these days. Skating is an awesome sport and requires mental and physical use. Your parents are thinking of sterio-typical street skaters. Remind them that there are some pros out there who are doing really amazing things.
