The current vision for science education is to improve learning for all students by enacting teaching practices that make rigorous science content accessible to diverse learners. Science education, as a field, is shifting focus to be practice-based and equity-centered as students and their ideas become the focal point of the profession. The enactment of this vision calls for professional learning opportunities for teachers that support sense making and enactment of reform-based practices. This design-based study is an exploration of how ten science teachers negotiate issues of equity and professional agency in their teaching of the science and engineering practices through identified problems of practice. Using qualitative methodology, I describe a critical professional learning model, a collaborative online community of practice, and the productive tensions that emerged. Some participants demonstrated that they could focus on the Science and Engineering Practices with attention to equity when they made purposeful decisions to center their students in the everyday decisions of teaching. Those with the autonomy to enact shifts to their teaching selected high leverage practices as tools for centering student ideas and cultural experiences. This study contributes to the gap in understanding about support for in-service teachers taking up equity practices in their work and responds to the call for teachers to explore innovations to their teaching in collaborative spaces. [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.]