Supplemental instruction (SI) is an academic support model developed by Deanna Martin at the University of Missouri–Kansas City (UMKC) in 1973 that uses peer-assisted study sessions to improve student retention and success within targeted historically difficult courses. The SI program provides peer support by having students who succeeded in traditionally difficult academic courses (e.g., Organic Chemistry, Biology 101, Logic) help other students complete these courses. SI is a non-remedial approach that provides regular review sessions outside of class in which students work collaboratively by discussing readings, comparing notes, working together to predict test items, and sharing ideas for improving class material. Courses selected for SI tend to be "gatekeeper" courses for first and second year students—generally those classes that have a 30% or higher proportion of students who receive a "D", fail, or withdraw (the DFW rate) from the course. Out-of-class review sessions are led by "SI leaders", students who took the class already and did well. SI leaders attend all class lectures, take notes, and act as models to those currently taking the course. The SI model is used for selected courses at the undergraduate, graduate, and professional school levels, and has been adopted by colleges and universities in the United States and internationally.