This research considers the innovative educational strategy known as the liquid learning system, which allows students attending classes either online or face-to-face. This system was implemented for the first time at a private European university in 2020 as a reaction to the Covid-19 pandemic. Emphasis is placed on the effect of the online choice on student academic performance. Using Instrumental Variables to control for self-selection bias, our findings show a significant gap in the form of lower grades for online students. Quantile regressions reveal that those in the lower tail of the grade distribution are the most adversely affected