Does lecture attendance affect academic performance? Panel data evidence for introductory macroeconomics

I analyze data from students enrolled in an introductory macroeconomics course taught at a public university in Italy to assess the impact of lecture attendance on academic performance. Using proxy variables regressions to capture the effect of unobservable student traits possibly correlated with attendance, I still find a positive and significant effect of attendance. However, when using panel data fixed effect estimators to eliminate time-invariant individual-specific unobservables, the effect disappears. The robustness of my results to supplementary data from a major public university in Spain suggests that the positive effect of attendance commonly reported in the literature may still incorporate an impact of unobservable student traits.