Class Size, Learning, and Knowledge Decay

Students may suffer from learning loss between the spring and fall semesters, an experience often called ‘summer learning loss’ or ‘knowledge decay.’ Although many studies examine knowledge decay in K-12, only a few examine college students. This study expands the literature by examining whether varying class sizes aggravate or dampen the loss of knowledge. We utilize a dataset on college students to analyze how class size affects knowledge decay using paired prerequisite and follow-on courses. We find that when a student takes larger prerequisite classes waiting longer to take the follow-on course raises grades. This finding is consistent with the hypothesis that students learn less in larger class sections, leaving them with less knowledge to decay. The analysis also provides novel estimates of the relationship between class size and learning: holding the number of terms between courses constant, students enrolled in larger prerequisite classes earn similar grades in subsequent courses.