This report examines the ways that credit-based transition programs (CBTPs) may help middle- and low-achieving students enter and succeed in college. It highlights promising practices used by CBTPs to help students who might have been considered noncollege-bound prepare for college credit course work. The report also discusses the challenges that CBTPs face when trying to include such students. The research for this report was conducted in the spring and fall of 2004. Case studies were undertaken in five states: California, Iowa, Minnesota, New York, and Texas. Two dual enrollment programs, an MCHS (Middle College High School), an International Baccalaureate program, and a Tech-Prep program were studied. The first section of the report describes the sites and examines some of the ways in which contextual features influence program implementation. The report then highlights findings regarding four key program features--student recruitment and selection processes; curriculum; support services; and data collection and use. For each feature, the researchers investigated the current practices of the case study sites, identified those practices that seemed most promising in meeting the needs of middle- and low-achieving students, and identified barriers to implementing them. An appendix presents more detailed profiles of each research site. Recommendations for policymakers and practitioners include: encourage broad student access; build strong collaborative relationships; and work with researchers to gather outcomes data. (Contains 19 exhibits and 10 footnotes.)