 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.