Under normal circumstances, when students invest more effort in their schoolwork, they generally show evidence of improved academic achievement. But when universities abruptly transitioned to remote instruction in Spring 2020, instructors assigned rapidly-prepared online learning activities, disrupting the normal relationship between effort and outcomes. In this study, we examine this relationship using data observed from a large-scale survey of undergraduate students, from logs of student activity in the online learning management system, and from students’ estimated cumulative performance in their courses (n = 4,636). We find that there was a general increase in the number of assignments that students were expected to complete following the transition to remote instruction, and that students who spent more time and reported more effort carrying out this coursework generally had lower course performance and reported feeling less successful. We infer that instructors, under pressure to rapidly put their course materials online, modified their courses to include online busywork that did not constitute meaningful learning activities, which had a detrimental effect on student outcomes at scale. These findings are discussed in contrast with other situations when increased engagement does not necessarily lead to improved learning outcomes, and in comparison with the broader relationship between effort and academic achievement.