Conviction is easier to borrow later if someone helped you build it early. Teenagers do not need a louder speech. They need a person who will open Scripture with them before the pressure arrives.
Start the conversation
Ask what they are afraid to lose. Then read Matthew 7:24 together. A house on the rock is not a mood. It is a practice: hear, and do.
Leave them with one verse they can repeat at school. Proverbs 3:5 is enough for a week.