This study investigated test-taking engagement on the Spring 2019 administration of a large-scale state summative assessment. Through the identification of rapid-guessing behavior -- which is a validated indicator of disengagement -- the percentage of Grade 8 test events with meaningful amounts of rapid guessing was 5.5% in mathematics, 6.7% in English Language Arts (ELA), and 3.5% in science. Disengagement rates on the state summative test were also found to vary materially across gender, ethnicity, Individualized Educational Plan (IEP) status, Limited English Proficient (LEP) status, free and reduced lunch (FRL) status, and disability status. However, school mean performance, proficiency rates, and relative ranking were only minimally affected by disengagement. Overall, results of this study indicate that disengagement has a material impact on individual state summative test scores, though its impact on score aggregations may be relatively minor.