Little evidence exists regarding students' actual use of testing time in naturalistic settings, particularly in the context of state accountability assessments. This study investigates students' test completion time and performance in the context of a statewide, English Language Arts and Mathematics computer-based assessment administered in grades 3-8. Results showed that in most grades, most students completed their ELA tests within the recommended time and their Mathematics tests in less time than recommended. Accounting for student demographic and prior achievement factors, we found a modest, positive effect of testing time on student performance in both subjects. The size of this effect gradually increased with advancing grade levels. We also found significant effects of gender and race/ethnicity on testing time controlling for prior achievement. Test interruptions, while rare, had a variable impact on student performance, reducing ELA scores by up to three points in some grades, with mixed effects observed in Mathematics. Finally, we found notable differences in the number of interruptions comparing student groups based on gender and race/ethnicity and controlling for testing time. We conclude with recommendations for policymakers to further enhance test administration practices and support equitable testing conditions.