As online learning expands in response to COVID-19, concerns about students' negative learning attitudes in online classes and educational gaps are increasing. Therefore, this study focuses on the influence of peers on changes in students' learning attitudes in online classes and academic achievement, which can be a mechanism that caused educational gaps during COVID-19. First, we empirically examined the change in the relationship between the learning attitudes of peers in school and individual students' learning attitudes and academic achievement. We also verified whether the influence of learning attitudes of peers in school differs depending on students' achievement levels. For the analysis, we used the first through sixth wave data of the Busan Educational Longitudinal Survey (BELS) and exploited propensity score matching methods to ensure homogeneity between the treatment and control groups. Afterward, the zero-inflated ordered probit model and the difference-in-difference-in-differences model were applied. We found that shifting face-to-face classes to online classes had a significant negative relationship with students' direct disruptive behavior (talking, disrupting with words and actions) and a significant positive relationship with indirect class disruptive behavior (doing other homework). Also, in online classes, peers' direct disruptive behavior in school was positively correlated with students' direct disruptive behavior (making noises), and peers' indirect disruptive behavior in school was negatively correlated with students' direct disruptive behavior (making noises). Finally, peers' direct disruptive behavior in school significantly negatively correlated with students' academic achievement, but this tendency was evident only in high academic achievers. Based on this, this study derived policy implications for improving the effectiveness of classes in digital conversion education in the future.