The disruptions to schooling created by the COVID-19 pandemic prompted nationwide concern about negative impacts on academic proficiency, particularly for vulnerable student populations. Pennsylvania's 2021 statewide assessments offered the first opportunity since the pandemic began to assess how students across the Commonwealth were faring, whether achievement gaps had widened, and how remote learning affected student performance. As in other states, the raw assessment data did not tell the full story of the pandemic's impacts on academic proficiency. Fewer Pennsylvania students participated in the 2021 assessments than in prior years, and test takers were not a representative sample of all students. In addition, test administration dates varied widely across the state in 2021, with some local education agencies (LEAs) postponing the usual spring assessments to the fall. Using a predictive model that accounts for the unique assessment issues in 2021 and the instructional modes that Pennsylvania LEAs offered, this research brief provides a fuller picture of the pandemic's impacts on academic proficiency in grades 5 through 8. Key findings for Pennsylvania students in grades 5 through 8 include: (1) students in vulnerable groups and in fully remote learning had lower assessment participation rates than other students in 2021; (2) the pandemic led to a substantial reduction in academic proficiency statewide in 2021, reducing academic achievement even more than the results for tested students indicated (3) the pandemic had consistently large negative academic effects across student groups, including for vulnerable groups that had low rates of proficiency before the pandemic; and (4) LEAs that were fully remote after winter break saw lower proficiency rates in 2021, compared with LEAs that offered fully in-person learning to similar students. [This brief includes contributions from Candy Miller, Rhonda Johnson, and Rosemary Riccardo.]