Studies on blended education pay little attention to implementation, thus limiting the understanding of how such programs contribute to student math learning. This article examines the implementation of a widely used blended algebra curriculum and the relationship between implementation and student outcomes. The study was conducted in 74 middle schools and 73 high schools in 51 school districts located in seven states. The study included both treatment and control schools. The blended-curriculum combines inquiry-based teaching and learning with technology (math software). The study found that teachers implemented the blended curriculum with low fidelity. Teachers had most difficulty allocating the recommended amount of time for the math lab and content. The study also found that the blended-curriculum teachers in the second year reverted to more traditional approach to instruction and spent less time on inquiry based instruction than in the first year, although they continued to use this approach at a higher level than teachers in the control schools. The study findings suggest that teacher adjustment of instruction in the second year, specifically balancing the amount of traditional instruction with inquiry instruction, in combination to the use of the math software contributed to the performance of the program.