This mixed method study investigated the impact of various levels of professional development (PD) on middle school educators' knowledge of second language acquisition (SLA) and the needs of English Language Learners (ELLs). This study also investigated participants' reasons for choosing their selected level of participation and their feelings about their abilities to implement what they had learned into practice. All study participants (n = 23) attended face-to-face traditional training. After the traditional training, participants could choose from the following options during the next twelve weeks: (a) no additional training, (b) virtual training, or (c) virtual training and use of application materials. Before any training began, all participants completed a pretest. At the conclusion of the twelve-week period, all participants completed a posttest. Following the posttest, volunteer participants were interviewed about their reasons for their selection of training levels and about their experiences with ELL/SLA PD. A statistically significant increase in knowledge was observed across all participants. The largest changes were observed for the material addressed within the traditional training. Similarly, most participants in this study reported a preference for in-person PD. Finally, despite increases in their knowledge about the needs of ELLs and SLA, participants reported they felt that barriers existed to changing practices. Recommendations for future research and implications for practice are discussed. [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.]