Since 1991, we have been using Alan Van Heuvelen's Overview, Case Study: Physics (OCS physics) methodology in introductory physics courses at New Jersey Institute of Technology (NJIT) with remarkable success. With the OCS method, physics concepts are presented first, with no mathematics. Only after the concepts are understood is math brought into the picture at the appropriate level. In addition, much of the learning is accomplished with students working together in small groups of three or four. In these collaborative settings, students actively engage each other in the learning process, working on specially designed small group problems, while the instructor acts as a facilitator of the on-going learning. We present various comparisons showing the effectiveness of OCS instruction over traditional teaching. In particular, since the introduction of OCS physics into NJIT's summer Educational Opportunity Program (EOP), which involves mostly minority students, EOP students have significantly outperformed non-EOP students in their fall physics courses. Interviews with students and observations of videotapes suggest that "second teaching" takes place in small groups following "first teaching" by the instructor. Second teaching is interpreted on the basis of ideas developed by Vygotsky.