The United States lags behind other countries in science education outcomes, even though STEM fields contribute to our economic growth and output. The challenge of improving science education and reducing achievement disparities has been especially pervasive in diverse urban centers such as New York City. In that vein, New York City has embarked on the implementation of a new set of standards, based on the Next Generation Science Standards (NGSS), that call for all students to engage in the three dimensions of science learning in service of explaining phenomena and solving problems. This study employed a phenomenological case-study approach to understand how teachers, who had participated in a sustained professional learning community, leveraged routines to implement NGSS-aligned instruction after the professional learning supports had been removed. The theoretical framework was drawn from studies that suggested high leverage practices, such as routines, can support ambitious teaching if embedded within professional learning that incorporates situated and proximate learning opportunities. Qualitative data were collected and coded for each of the three case study participants including individual interviews, focus group discussion, and transcripts of classroom observations. The findings indicated that the teachers believed the routines were supportive in increasing student engagement and equity and were valuable tools in NGSS implementation. The participants found the immersive and collaborative professional learning valuable in unpacking the NGSS. However, little evidence was observed for the implementation of routines or NGSS-aligned instruction in two of the three cases. The lack of transferability of the routines to new contexts may be due to significant contextual barriers such as time constraints, lack of administrator buy-in, deficit views of students, and the misalignment between the standards and high-stakes standardized exams. This suggests that critical barriers may lead to the compartmentalization of pedagogical beliefs when educators are facing pressures and messaging that lack coherence with the professional learning framework. These findings have implications for state and district policy makers to ensure the alignment of standards, curriculum, instruction, and assessment. Science educators may find well designed unit-level and instructional routines a useful tool in supporting NGSS implementation. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]