The purpose of this technical appendix is to share detailed results and more fully describe the sample and methods used to produce the research brief, "COVID's Impact on Science Achievement: Trends from 2019 through 2024. We investigated three main research questions in this brief: 1) How did science achievement in 2021 and 2024 compare to achievement in 2019, before the pandemic? 2) How much additional schooling was required in spring 2021 and spring 2024 to return to spring 2019 levels? 3) How do these patterns differ by race/ethnicity?