Online courses have expanded rapidly and have the potential to extend further the educational opportunities of many students, particularly those least well-served by traditional educational institutions. However, in their current design, online courses are difficult, especially for the students who are least prepared. These students' learning and persistence outcomes are worse when they take online courses than they would have been had these same students taken in-person courses. Continued improvement of online curricula and instruction can strengthen the quality of these courses and hence the educational opportunities for the most in-need populations.