DEAR AMY: My 18-year-old son started college this year. He has a part-time job and is paying for a new car to drive to school 30 miles from home. He lives at home, but makes bad choices by smoking pot! I have asked him to stop many times but he chooses to continue to smoke. I need advice as to what to do or how to stop the rage that blows up when he does this in my house. I know if I kick him out and take the car away, he will drop everything he's been working for.

-- Disgusted Dad

DEAR DAD: I understand the parental fear that your child will essentially punish himself (drop out of school, etc.) to defiantly declare that "you're not the boss of me." At 18, your son's brain is still growing and developing -- which provides an explanation for his behavior -- as well as a great reason not to smoke pot (his brain still needs time to mature).

If your goal is to keep him at home during this maturing phase, you should appeal to his semi-independent self by talking about this rationally.

Choose a time to discuss this when you are both in a good frame of mind.

Tell your son, "You know I don't want you to smoke pot. It is illegal in this state. You are underage. It fries your brain. I realize I cannot control your every move, but I cannot tolerate you using at home. This might not seem reasonable to you, but that's the way it is. Do you understand?" Give him time to respond.

Then you should tell him, "Here's how it's going to be. If I find out you are using, you're going to have to move out. I don't want this to happen because I really like having you here. But you're making choices, and I have to make choices too." He may test you, and you should be prepared to calmly tell him to pack a bag. He may bounce back and forth a couple of times. Continue to support his efforts at school and work. You are both going through a process; he needs to grow up and you need to let go.