One day, in a lousy school, a teacher walks into class and tells the students never to smoke. Then she takes out a cigarette and smokes throughout the whole lesson.
The next day, she walks into class and tells the students never to drink alcohol. Then she takes out a bottle of beer and drinks it throughout the lesson.
The day after, she walks into class and tells the student to never abuse inhalants. then she takes out a bottle of glue and sniffs it throughout the whole lesson.
At the back of the class, one student says to another, "Ican't wait till she tells us to refrain from adultery..."