The Next Generation Science Standards (NGSS) advocate an integrated model of science instruction for middle schools in which the science disciplines are connected rather than separate. This model, used by other countries that are consistently successful in science, has several key benefits, including enhanced student learning and better preparation for the new California Science Test (CAST). The California Board of Education voted in 2013 to make integrated science the state's "preferred" model. The K-8 NGSS Early Implementers Initiative was designed to support middle school science teachers and their administrators in integrating the sciences. From the start of the Initiative, all participating districts adopted the state's integrated science model. This fifth Early Implementer evaluation report examines how schools and districts in the Initiative are negotiating the transition to the integrated science model. The report draws on substantial data collected from teachers, administrators, and Initiative leaders through surveys, interviews, and classroom observations. This report also provides two detailed examples of integrated instruction through vignettes of classroom observations conducted in grades 6 and 8.