In addition to balance tests, we perform placebo tests in which we examine the effect of exogenous GP matches at ages 20 to 25 on educational outcomes at the compulsory and high school levels and the effect of GP matches at ages 17 to 20 on educational outcomes at the compulsory school level. The vast majority of people aged 20 to 25 have completed high school, and the vast majority of those aged 17 to 20 have completed compulsory school. Thus, GP matches after age 19 should not affect compulsory and high school outcomes, and GP matches after age 16 should not affect compulsory school outcomes. Looking at the results in table 7, we see that all estimates are much smaller or in the wrong direction and none are statistically significant. These results are inconsistent with the presence of biases due to nonrandom sorting of children to GPs of a specific gender, and support a causal interpretation of our results.27

Table 7.

Placebo Tests; Post-High School GP Swaps

High school academic trackHigh school STEMM credentialCompulsory school STEMM GPAHigh school STEMM GPA
A: All girls who were subject to their first exogenous GP swap between ages 20 and 25 
Same-sex GP 0.008 −0.005 −0.030 −0.022 
 (0.017) (0.018) (0.039) (0.036) 
Mean 0.759 0.199 4.120 3.986 
Observations 6,730 6,730 6,730 6,730 
B: All girls who were subject to their first exogenous GP swap between ages 17 and 20 
Same-sex GP −0.007  −0.028  
 (0.010)  (0.023)  
Mean 0.741  4.199  
Observations 16,868  14,862  
High school academic trackHigh school STEMM credentialCompulsory school STEMM GPAHigh school STEMM GPA
A: All girls who were subject to their first exogenous GP swap between ages 20 and 25 
Same-sex GP 0.008 −0.005 −0.030 −0.022 
 (0.017) (0.018) (0.039) (0.036) 
Mean 0.759 0.199 4.120 3.986 
Observations 6,730 6,730 6,730 6,730 
B: All girls who were subject to their first exogenous GP swap between ages 17 and 20 
Same-sex GP −0.007  −0.028  
 (0.010)  (0.023)  
Mean 0.741  4.199  
Observations 16,868  14,862  

The table shows the β1 coefficients obtained through estimation of equation (1) as described in the text and reproduced here for clarity: yi=α+β1GP_Matchi+τt+πm+θc+ρd+εi. yi is a general term denoting the outcome listed at the top of each column, and each estimation includes municipality (πm), year of swap (τt), birth year (θc), and previous GP (ρd) fixed effects. The point estimates depicted in the table should be interpreted as the effect of random assignment to same-gender GP in childhood on the outcome listed at the top of the column. Standard errors are clustered at the level of the exogenously assigned GP. The sample in panel A includes all girls who were subject to their first exogenous GP swap between ages 20 and 25. The sample in panel B includes all girls who were subject to their first exogenous GP swap between ages 17 and 20. Significant at *10%, **5%, ***1%.

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