First publicized and marketed in 1976 by developer Lee Canter, Assertive Discipline is a well-respected and widely used program. According to Render, Padilla, and Krank, over half a million teachers have received AD training (1989). AD focuses on the right of the teacher to define and enforce standards for student behavior. Clear expectations, rules, and a penalty system with increasingly serious sanctions are major features. Some research (e.g., Mandlebaum and McCormack) is supportive, but most is inconclusive about the effectiveness of the AD approach (Emmer and Aussiker, Gottfredson, and Render, Padilla, and Krank).