In this mixed-methods research study, the researcher investigated the impact of professional development training using the University of Notre Dame's "English as a New Language (ENL) Online Professional Development Modules" (Lichon, Dees, & Roach, 2017) on teacher and administrator efficacy in teaching English language learners (ELs) and serving their families in six Catholic schools. The research findings revealed teachers increased their efficacious beliefs about their ability to teach ELs through the focused training in language acquisition, evidence-based instructional strategies, and culturally sustaining pedagogy. Findings further revealed increased cultural competency promoting proactive inclusionary practices by the schools' principals and satisfaction by parents because of demonstrated practices and dispositions. Students' standardized achievement scores in English, reading, and language arts indicated significant gains. [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.]