Excerpt: “Although national test scores provide clear evidence on student achievement across time, they do not illuminate what is driving gains or losses. Nonetheless, careful examination of test scores can corroborate some explanations for changes in student achievement and discount others. This report examines recent trends in US student achievement, as measured by national and international assessments, and identifies four key trends that any satisfactory explanation of recent US student performance should account for: a downward trend beginning around 2013; declines driven by the bottom half of the distribution, both before and after the pandemic; higher absolute achievement gap growth in the US than other nations; and adult assessment trends that closely match those of students. The report concludes by evaluating how common explanations of student achievement trajectories align with these trends.”