The "Illinois Charter School Biennial Report" for the 2019-20 and 2020-21 school years was originally published in January 2022 but was incomplete. The COVID-19 pandemic interrupted the normal administration and reporting of statewide student performance data during this time period. More specifically, ISBE received a statewide waiver of all federally required assessments, summative designations, and reporting on accountability metrics on the Illinois Report Card for the 2019-20 school year and allowed districts to select between two assessment windows (spring or fall 2021) for the 2020-21 school year. Accordingly, only partial data was available for the 2020-21 school year at the time of this report's initial release. ISBE republished school year 2020-21 data that included districts that selected the fall 2021 testing window on July 21, 2022. This Addendum reprints the charts included in Section 5 of the original report updated with complete academic data for the 2020-21 school year. [For "Illinois Charter School Biennial Report. 2019-2020, 2020-2021," see ED618454.]