Reality Rhyner, teachers typically sign contracts agreeing to a drug, alcohol, and tobacco free environment at school. Teachers can get fired for bringing any of those to work or if they come to work impaired. They can also be drug tested if there is a reasonable suspicion that a teacher is on drugs. 

Perhaps all teachers should have to go to the principal's office twice a day and blow into a breathalyzer for you too, Richard. Funny how some cons like to look for ways around that silly ole Constitution. Now if we could just make sure that everyone with a firearm would have to take your drug test too. Yep, that would be "pathetic" too.