This qualitative case study investigated the implementation of the Next Generation Science Standards (NGSS) by sixth-grade teachers in diverse educational settings within the Central Valley of California. The research focused on identifying the practical successes and ongoing challenges faced by educators in elementary and middle school environments, a decade after the adoption of NGSS. Employing a mixed-method approach that includes interviews, classroom observations, and document analysis, the study provides a comprehensive view of how structural differences between school types affect the adoption and effectiveness of NGSS. The findings indicated that teachers are actively striving to create student-centered, inquiry-based learning environments that encourage scientific exploration and critical thinking. However, significant barriers persist, particularly related to resource constraints and insufficient professional development opportunities. Many educators report the need to use personal resources or makeshift materials due to a lack of adequate school supplies, which hampers their ability to deliver comprehensive science education effectively. The study's implications highlight the critical need for systemic changes in how educational resources and professional development are provided. It suggests that educational policy makers and school administrators should consider more robust support systems that include targeted professional development tailored to NGSS implementation and equitable resource distribution across different school settings. By addressing these areas, the educational sector can enhance the capacity of teachers to engage students in meaningful scientific inquiry, ultimately leading to improved student outcomes in science literacy. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]