Closed laboratories are becoming an increasingly popular approach to teaching introductory computer science courses. However, as observed in [1], “Considering the prevalence of closed labs and the fact that they have been in place in CS curricula for more than a decade, there is little published evidence assessing their effectiveness.” In this paper, we report on how students’ performance in closed laboratories relates to their performances on a placement exam, homework assignments, course exams, and how it relates to their self-reported attitudes towards our CS1 course. This analysis provides insights to help us improve the