Objective: Researchers have speculated that the COVID-19 pandemic may expand the academic performance gap experienced by at-risk students. We examined learning experiences during the 2020-2021 school year and the impact the pandemic has had on high school student grade point average (GPA), including predictors of change in GPA from 2019-2020 to 2020-2021. Method: Participants were 238 adolescents (55.5% male), 49.6% with attention-deficit/hyperactivity disorder (ADHD), in the United States. Adolescents reported on their GPAs via online surveys. Results: GPA significantly decreased on average from 2019-2020 to 2020-2021 school year. ADHD status and biological sex significantly moderated change--students with ADHD and male students reported decreased GPA, whereas students without ADHD and female students' GPA did not change. Low income and Black/Latinx students had lower GPAs in both school years. Conclusion: It is imperative that additional supports be provided for at-risk students to help them catch up on missed learning during the pandemic. [This paper was published in "Journal of Attention Disorders" v26 p1011-1017 2022.]