We begin by estimating the effects of teaching repetition on standardized grades. The estimates in column 1 of table 3 support the conclusion that instructors cannot take experience gained in one section, and quickly apply it in subsequent sections in a way that improves student performance. Average grades in instructors’ second sections are actually lower than in their first, but the decrease is less than 1 percent of a standard deviation and not statistically significant. The 95 percent confidence interval of this estimate allows us to rule out effects below −5.1 percent and above 3.4 of a standard deviation. For comparison, Williams and Shapiro (2018) find a 3 percent of a standard deviation improvement in average student grades for instructors’ second section compared with their first.6 Similarly, De Vlieger, Jacob, and Stange (2018) find that students perform 3 to 4 percent of a standard deviation better on the final exam if the instructor has taught the course at least once before.

Table 3.

The Effects of Teaching Repetition on Student Outcomes

Dependent Variable(1)(2)(3)(4)
2nd section −0.008 0.004 0.050 −0.302
(−0.051 to 0.034) (−0.008 to 0.016) (−0.065 to 0.166) (−1.123 to 0.519)
3rd section 0.012 0.008 0.083 −0.839
(−0.064 to 0.087) (−0.014 to 0.030) (−0.118 to 0.284) (−2.226 to 0.548)
4th section 0.018 0.009 0.132 −1.159
(−0.088 to 0.124) (−0.021 to 0.040) (−0.142 to 0.407) (−3.135 to 0.816)
Observations 77,269 83,195 27,144 26,918
R2 0.569 0.290 0.551 0.412
Section 1 average outcome .028 .072 −.033 14.415
p-value joint significance of all section variables .4221 .9020 .7966 .5536
Dependent Variable(1)(2)(3)(4)
2nd section −0.008 0.004 0.050 −0.302
(−0.051 to 0.034) (−0.008 to 0.016) (−0.065 to 0.166) (−1.123 to 0.519)
3rd section 0.012 0.008 0.083 −0.839
(−0.064 to 0.087) (−0.014 to 0.030) (−0.118 to 0.284) (−2.226 to 0.548)
4th section 0.018 0.009 0.132 −1.159
(−0.088 to 0.124) (−0.021 to 0.040) (−0.142 to 0.407) (−3.135 to 0.816)
Observations 77,269 83,195 27,144 26,918
R2 0.569 0.290 0.551 0.412
Section 1 average outcome .028 .072 −.033 14.415
p-value joint significance of all section variables .4221 .9020 .7966 .5536

Notes: All regressions include fixed effects for instructor-course-parallel-course combinations and section starting time, cubic polynomials for student grade point average and age, and indicators for student gender and nationality. 95 percent confidence intervals based on standard errors clustered at the course level are in parentheses.

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