This article reports results from a scale-up study of the impact of a software tool designed to support teachers in the digital learning era. This tool, the Curriculum Customization Service (CCS), enables teachers to access open educational resources from multiple providers, customize them for classroom instruction, and share them with other teachers. The study involved 73 Earth science teachers and their students in five U.S. school districts, and examined impacts of CCS deployment on teachers' attitudes and practices--as well as their students' learning gains--over the course of one school year. Results are reported in two parts: the "impact" study included all teachers, while the active user study examined the usage patterns of teachers who actively used the CCS following the use-diffusion framework. Results from the two studies revealed complementary results. Teachers in the "impact" study reported significant increases in their awareness of other Earth science teachers' practices and in their frequency of using interactive resources in their instruction. Results also suggested that there were contextual differences between school districts that affected teachers' use of the CCS. Results from the "active user" study showed much less of a connection between teachers' CCS usage patterns and their reported attitudes and practices. However, the students of teachers who showed the most variety in their use of the CCS had significantly higher learning gains. In addition, these teachers' use of the CCS tended to benefit student populations that had a larger portion of low socio-economic status students across all user typologies and other measured demographics.