The Covid situation has converted an already  important issue- how to deliver lectures well online- to an urgent one. Several years ago we began the Coordinated Online Learning (COOL) project in Stat 100 and Stat 200. Careful records were kept of the outcomes over 4 semesters in which one teacher taught both versions. The system is simply to allow students to watch the recorded in-person lectures on their own time on the Web. In Stat 200, the in-person class is also allowed full access to the online lectures. Despite that, the online students have done better on objective computer-graded exams. After adjusting for a variety of potential confounders (ACT scores, high school GPA, etc.) the estimated average treatment effect of omitting in-person lectures is still slightly positive, although not statistically significant. We discuss what we think were the preconditions for making the purely online lectures successful.