As the 2020-21 school year opens amid the COVID-19 pandemic's disruption, this third and final installment of Quality Counts 2020 delivers a data-driven portrait of the nation's school system along with A-F grades and rankings for each state on a wide range of academic, school finance, and socioeconomic indicators. This report also includes an exclusive Coronavirus Learning Loss Risk Index using recent U.S. Census Bureau data to weigh states' educational vulnerability in key areas, in addition to the first full update of Quality Counts' K-12 Achievement Index since 2018. Articles in this issue's Quality Counts report include: (1) Nation's Schools Receive a 'C' As Pandemic Turns Up the Heat (Sterling C. Lloyd and Alex Harwin); (2) COVID-19 Learning Loss Index Reveals Big Equity Problems (Alex Harwin and Yukiko Furuya); and (3) Nation Shows Mediocre Academic Performance as Pandemic Continues (Sterling C. Lloyd and Xinchun Chen). [For the first installment of Quality Counts 2020, see "Quality Counts 2020: Chance for Success. Education Week. Volume 39, Number 19" (ED604437). For the second installment, see "Quality Counts 2020: School Finance. Education Week. Volume 39, Number 33" (ED605585).]