Don't force them. let them know what is good and bad and leave the rest to them to decide.
Respect them as you respect others , not in words but in actions.
Don't tell them that they are useless. Tell them that they are "used less". Allow and encourage there talents to grow.
Think how you felt as a teen when your parents or elders behaved in a particular way, and you adjust accordingly.
Put them to Art of living Yes + course. I have seen miraculous transformations in youth.