US public schools often do not provide multilingual (ML) students with the support necessary to be successful in science education or deny ML students the opportunity to participate altogether. Recent science and English Learner Development (ELD) standards adoptions in California require teachers to change their practices, creating the potential to improve educational opportunities for ML students. Professional Development (PD) is often used as the method to achieve teacher change in practice. However, PD does not always achieve its intended outcomes. To narrow opportunity gaps for ML students, it is vital to understand the ways in which teachers learn from PD, and how their learning influences their ML students' learning. This multiple case study used a critical sociocultural theory lens to explore how upper-elementary teachers participating in The Science Project translated their PD learning into practice to create more equitable conditions for their ML students, and the ways in which students responded. The findings highlighted the complexity of teacher learning, which must be understood within context. Three catalysts were found to move teachers toward shifts in instructional practice: (1) relationships; (2) teacher agency; and (3) experiential, hands-on learning; which over time, led to shifts in beliefs about teaching and learning. The ways that ML students responded exceeded their teachers' expectations. However, contextual factors and the levels of support teachers provided played a large role in how ML students were able to utilize the learning opportunities teachers' implementation of PD learning created. [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.]