In a large school district in Florida, many third-grade students have been retained over a 7-year period. Enrollment documents, such as summer school registration forms and seven annual summer reading camp evaluations in 2013-2019, indicated that 13,693 students attended the 4-week summer reading camp during this period. Summer reading camps are implemented as a final means to enable students' promotion to fourth grade. According to Florida Statute 1008.25(6) F.S., if third-grade students are not proficient by the end of the school year, they must be retained. Promotion is granted if students attain an achievement level of 2 out of 5 or higher on the state-mandated English Language Arts assessment or if they attain passing grades in summer reading camp. Limited research exists on third-grade retention and the factors that impact reading performance of retained students. In this mixed-methods sequential, explanatory study, for the quantitative component three demographic factors were examined for their interactions on students' final reading score after the summer camp. In a series of 2 x 2 x 2 factorial analyses, these were students' gender, socioeconomic status, and the status of English Speakers of Other Languages in relation to their scores on the Stanford Achievement Test-10. The statistical results of seven null hypotheses revealed that none were rejected. The qualitative component was comprised of individual interviews with seven elementary school principals in the school district for their perspectives on retention and assessment of third-grade students. The researcher guided the interviews with semi-structured, open ended questions. Seven themes were extracted that promote understanding of principals' perspectives: (a) views on assessment and retention, (b) student performance, (c) closing the achievement gap, (d) teachers, (e) summer reading camps, (f) emergence of COVID-19, and (g) recommendations for assessments and retention. Retention has been controversial, and, based on the study results, additional research is called for, especially with regard to the seven hypotheses. This study will contribute to the body of research on third-grade retention to inform teachers, parents, administrators, and policymakers of some of the primary causes of third-grade retention and recommendations because of the current accountability and renewed interest in grade retention and high-stakes testing. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]