The purpose of the present study was to gather summative and formative data related to the implementation of Zearn Math during the first year of a two-year study. The sample included students in a large urban school district comprised of predominantly African American (58%) and Hispanic (28%) students. Roughly 90% of students are economically disadvantaged. As of the 2016-17 school year, only 8% of the district's students in Grades 3-8 met mathematics proficiency levels as compared to 40% of all students in the state. The current research was conducted during the district's second year of implementation of Zearn Math. During the 2016-17 school year, the district piloted the curriculum in two schools and provided some implementation support. The following year, 15 elementary schools began learning with Zearn Math and implementing the rotational classroom model, while the remainder of the elementary schools in the district continued to learn with EngageNY. This study explores the treatment schools' implementation of Zearn Math and the impacts of the shift during the first year of implementation.