Mommaprude--
Aside from the question of drug use by a minor under your roof, you have the problem of who is in charge in your house, you or the teenager.
I'm guessing that one reason you suspect drugs is uncooperative and anti-social behavior. House rules are ignored. You may be missing money or pawnable items.
Follow shewolf's suggestion and check out the kits at the drugstore.
Then tell your kid that s/he has choices: cooperate with you or you will call the police.
Quote:Would like to know how to test without teen knowing that it's being done.
Why without the teen knowing about the test? If you have a user, you have problems. If the teen is clean, you still have problems of trust and communication.
Start facing the problems--head on. Right now your house isn't a particularly pleasant place, is it?