This study examined the effect of mandated school closures during the COVID-19 pandemic on student learning loss and the effects of a rapid shift in instructional modality. The research study focused on comparing the academic year results of 2021-2022 to the year of 2018-2019 in English language arts and mathematics assessments, specifically using the California Assessment of Student Performance and Progress (CAASPP) statewide assessment, within Modesto City Schools in California. The study sought to determine if there were disproportionate academic achievement deficits among various student attribute groups, including socioeconomic status (SES), sex, students with disabilities (SWD), and ethnicity. By conducting a nonexperimental case study and utilizing secondary data analysis, the researcher accessed student assessment data from Performance Matters and employed the California Educator Reporting System (CERS) to extract relevant information. This study identified statistically significant gaps in student achievement outcomes for students with disabilities, students from lower socio-economic backgrounds, males in mathematics, and students in lower grade levels in ELA. These findings suggest that certain student groups may be more vulnerable to the negative effects of school closures and remote learning. The study also identified specific student characteristics, such as socio-economic status, disability status, and grade level, as predictors of academic achievement in both subjects. These findings emphasize the importance of addressing the achievement gaps that have emerged during the mandated school closures and providing targeted support to ensure equal opportunities for all students to succeed academically. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]