Fig. 37.
Heterogeneity by the previous usage for Jr. HS. The shaded region is the 95% confidence interval computed with standard errors robust to clustering at school level. Study time for students in grades 7 and 8 in a school with high usage minus study time for students in grades 7 and 8 in a school with low usage. The previous usage is defined by the average study time for students in a given school from April 2019 to December 2019. Low and High are defined by a student belonging to a school with the previous usage below median and above median, respectively