Schools are frequently inundated with demands to implement new instructional interventions and teaching methods that are not yet backed up by a solid body of research. Fortunately, many of these innovations include elements of more established strategies for which evidence of positive effects does exist. Guskey describes the core elements of one such well-established teaching method, mastery learning. He explains a number of its essential features--including diagnostic pre-assessment with pre-teaching, progress monitoring through regular formative assessments, and enrichment or extension activities--which are also incorporated into the Response to Intervention model.