This paper presents the results of a quasi-experimental study examining the effectiveness of Amplify Reading, a digital supplemental literacy curriculum that students play independently at school or at home, in improving student literacy outcomes as measured by end of year Dynamic Indicators of Basic Early Literacy Skills (DIBELS) Next for students in Grades K-2. Students in Amplify Reading outperformed and outgrew a comparison sample of students from their district. Significant and meaningful effects were obtained over one semester with an average of fewer than seven hours of use of the program. This is less than the expected use over the course of a school year, suggesting the potential of stronger impact when the program is used over a longer period of time.