OER Knowledge CloudJournal ArticleYe, LeiRecker, MimiWalker, AndrewLeary, HeatherYuan, MinThis 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 i2015Association for Educational Communications and TechnologyEducational Technology Research & Development63355-38010.1007/s11423-015-9377-610421629customizing instructioneducational resourceslearningOpen Educational Resourcesscience education – researchsoftware development equipmentstudent learningteacher practiceteacherstechnology usage