This study was a descriptive, mixed methods evaluation of a science professional development called Engaging Young Minds (EYM), for elementary teachers in Los Angeles. It was developed in response to the implementation of the Next Generation Science Standards (NGSS) and the summer 2016 session focused primarily on the NGSS Practice of Scientific Modeling. Participants included teachers who participated in the summer 2016 session as well as teachers who had participated in prior sessions. A total of 86 teachers completed a pretest-posttest survey during the 2016 session, 26 prior participants completed a single-administration survey, and ten teachers were interviewed at the end of the 2016-2017 school year. Survey data revealed that teachers reported significant improvements in their confidence following participation in EYM as well as expected changes to their classroom practice following EYM. Additionally, teachers showed significant growth in their understanding of scientific modeling during the summer 2016 session. Through interviews, teachers revealed that they were more likely to teach science, but their actual classroom practice changed little. The main change reported was in the area of student talk and student-led discussions; namely that this noticeably increased following EYM in 2016. Teachers did not retain as much understanding of scientific modeling as expected and implemented little scientific modeling practices in their classrooms during the 2016-2017 school year. Findings indicated that the transition to the NGSS in elementary classrooms was more complicated than originally anticipated. Additionally, while EYM was a higher-quality professional development opportunity for teachers, it led to little change in actual classroom practice. [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.]