The purpose of this Action Research study was to examine and improve the instructional practices and social-emotional learning for multilingual learners in third-grade, urban public school classrooms. Participants and data collected in Cycle 1 consisted of six interviews with third-grade classroom and special education teachers, three classroom observations of a content lesson specific to multilingual student achievement, and two post-observation student focus groups. Analysis of Cycle 1 interviews and observation of grade 3 educators led to the emergence of the following themes: the need for culturally responsive teaching practices to aid MLLs in accessing the content and the need to embed social-emotional learning practices in daily instruction. Action steps for a Multilingual Learner (MLL) instructional series were then designed, implemented, and evaluated for a second research cycle. Action steps included instructional and cooperative learning sessions with 3rd-grade educators, followed by professional learning observations. The sessions aimed to educate and inform 3rd grade teachers of the best practices for teaching MLL students and to provide educators with strategies to implement SEL instruction to increase MLL achievement and sense of belonging in the classroom. Findings from Cycle 2 action steps included the current curriculum not being culturally relevant to multilingual learners, student collaboration and implementation of Teaching English to Speakers of Other Languages (TESOL) strategies increased multilingual participation in the classroom, and lastly, peer observations improved instructional quality and student outcomes. Implications for the organization included integrating culturally responsive materials into the curriculum, increasing student opportunities for collaborative learning, and continued mentorship and peer observations for educators. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]