The problem addressed in this quantitative study was that the second-grade students in the selected school were performing low on the tests compared to other grade levels in the selected school district. The results from the investigation on the effect of blended instruction using the Zearn® Math curriculum on student achievement, the perception of teachers on the implementation of the Zearn® Math curriculum, its impact on student achievement, and the barriers will assist the leaders and teachers at the selected school to enhance student learning. The "cognitive theory of multimedia" by Mayer (2005) guided the study, and the research design of this study is based on a quantitative design. The existing data from four second-grade Math classrooms and the survey results from all the second-grade teachers in the district were collected to investigate the blended instruction using the Zearn® Math curriculum. The results reveal that more completion of Zearn® Math digital lessons increases the student achievement scores and that the high-completion group outperforms the low-completion group. A statistically significant relationship exists between the number of lessons completed, the time spent to complete the lessons, and the student achievement scores. The teacher reaction questionnaire responses by the teachers emphasize that there needs to be a focus on digital professional development, which helps the teachers to have a proper understanding of the successful implementation and positive impact of Zearn® Math blended instruction and several Zearn® Math features. [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.]