All teachers should be subjected to a drug test before they are allowed to be admitted into the school system. Just like any other job, teachers should also be subject to drug testing. No one would want their kids education being handled by someone who is currently on and using illegal drugs.
Although the idea we all have of a teacher is one of a non drug user, or abuser, we shouldn't take that risk with our children. Consider that people with addictions usually appear to function normally in their daily lives, and thus are not easy to spot, then you realize that a drug addict could be anyone. It is only a matter of time before a drug addict has problems associated with their addiction, and you wouldn't want it to be your childs teacher. Teacher should be drug tested prior to employment.