Student attendance is a predictive measure of success in brick-and-mortar schools with little research examining this relationship in online schools. This study explores students in online classrooms within online schools, to determine if the days a student was active on a course during the COVID-19 pandemic predicted success. A multilevel modeling found fixed effects for level-1 (days active, gender, ethnicity, free and reduced lunch), level-2 (class size, grade-level, and subject), and random slope for days active significant. School size did not improve the model. Student days active is a powerful predictor and offers insight into student success in online schools.