Drug tests are not voluntary inside my house. My son (17) and daughter (13) have known from the time they were old enough to understand that random drug screens would occur as a mater of business.

I have always told them (and followed thru) that if I test them, everyone in the house tests at the same time.

Sorry if that ruffles anyone's feathers, but I am basing that policy on the childhood I lived. Don't like it any way... Tough.