The California State Board of Education (SBE) adopted the California Next Generation Science Standards (NGSS) to transform science teaching and learning in K-12 schools in 2013. The new standards emphasize "three-dimensional learning": disciplinary core ideas, crosscutting concepts, and science and engineering practices. They are aligned with the Common Core State Standards to prepare students for college and careers. In this report, the authors leverage a survey conducted at the end of the 2016-17 school year to examine districts' implementation of the new standards. The authors find: (1) Implementation is uneven; (2) About half of districts have adopted the SBE's preferred models; (3) Instructional materials, science labs and equipment, teacher shortage, and teacher training present big challenges; and (4) Successful implementation may require changes in other elements of the K-12 system. The Next Generation Science Standards are an important step toward improving science education; however, the state needs to take additional steps to help districts implement NGSS and prioritize science education. The authors recommend several actions, including updating statewide high school graduation requirements, incorporating specific science metrics into the state accountability system, and leveraging NGSS to improve science education in the early grades.