The NGSS Early Implementers Initiative was created to help eight California school districts and two charter management organizations, supported by WestEd's K-12 Alliance, implement the Next Generation Science Standards (NGSS). Many educational initiatives are funded for only a couple of years. This unique initiative spanned an extraordinary six years, during which eight school districts worked toward districtwide implementation of the Next Generation Science Standards (NGSS), which call for teachers to transform their instructional practice. This 12th report in WestEd's evaluation series for policymakers, school and district administrators, and professional learning specialists describes the Initiative's scale-up in its later years to reach all K-8 science teachers. Specifically, the report addresses the following questions: (1) In contrast to focusing in Years 1-4 on developing Teacher Leaders, what strategies did districts use in Years 5-6 to reach all other K-8 teachers of science (called "expansion teachers" in this report)?; (2) What impacts has the Initiative had on expansion teachers?; (3) Which professional learning strategies have been most and least effective for influencing the practice of expansion teachers?; and (4) What special attention was paid to providing administrators with professional learning to prompt their support of NGSS implementation?