This study sought to understand teachers' perceptions of their effectiveness in teaching multi-lingual learners, MLLs, in their middle and high school classrooms. Participants were content, related arts, and career teachers who encounter MLLs every semester and endeavor to simultaneously teach content and academic language to students of varied educational histories. This research surveyed, observed and interviewed multiple teachers from various content areas to determine if teacher preparation programs and all they entail prepared them to teach MLLs. There is a growing body of research at the secondary level, but more needs to be done when dealing with older students in middle and high schools. Participants were asked to relay their training experiences and submit recommendations they perceived would benefit teachers. This research has several implications and suggestions for future studies. [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.]