This study explores the professionalization of a group of 28 pre-service teachers, using a qualitative case study design and reflective practice as the analytical framework. The pre-service teachers were involved in a service learning project at a local middle school in the U.S. where they designed and taught a content area lesson to English language learners (ELLs). After the lesson, the pre-service teachers analyzed their experience through a reflective essay assignment. Findings indicated that the pre-service teachers recognized the need to adapt their lessons for ELLs in varying degrees primarily in the areas of language and content support. Reflective practice as a component of the process of providing sheltered instruction of English should serve as an instrumental part of preparing teachers to work in diverse educational contexts.