The study provides compelling evidence on the impact of informal peer interactions on academic and behavioral outcomes, but a few aspects could use more clarification. While the methodology accounts for changes in bus routes to establish causal effects, were any sensitivity tests performed to ensure robustness against unobserved confounders, such as family relocation or school choice policies?
Moreover, the results suggest stronger peer effects in adolescence, particularly for behavioral outcomes. Could the authors discuss whether these effects persist over time? Do peer influences on the bus translate into long-term changes in student performance or social behavior beyond school years?