The number of English language learners in schools in the United States has dramatically increased in the last thirty years; today there are over 4.7 million English language learners (Fix & Passel, 2003). Researchers and theorists cite a range of skills and knowledge that all teachers should have in order to create optimum classroom conditions for English language learners (Lindholm-Leary & Borsato, 2006; Echevarria et al. (2004); Montecel & Cortez, 2002; Fillmore & Snow, 2002; Brisk et al., 2002; Nieto, 2000; Gonzalez & Darling-Hammond, 1997; Delpit, 1995; Chamot & O'Malley, 1994; Cummins, 1981). Despite the dramatic increase of English language learners, only a small proportion of K–12 teachers have received any type of professional development targeted for these students (National Center of Educational Statistics, 2002).

This qualitative case study examined how the development of a teacher professional development program called the English Language Learner Study Group affected teachers' understanding of the sociocultural, linguistic and instructional needs of English language learners and impacted the teacher's perceptions of their instructional practice. Eight volunteer teachers and one program leader engaged in three dimensions of professional development: formal classroom courses, monthly study group meetings and participation in a mentoring program targeting English language learners.

Data instruments included teacher interviews and questionnaires and researcher field notes. The principal findings from the study showed: (1) the professional development program dramatically improved the teachers' understanding of the sociocultural, linguistic and instructional needs of English language learners; (2) the teachers' perceptions of their instructional practice improved as a result of the program; (3) the lack of time emerged as an important factor in constraining teachers' professional growth; (4) panel discussions involving high school English language learners who shared their personal histories and school experiences enriched the teachers' understanding of the challenges that many English language learners face in schools.

Findings from this study are consistent with current research literature on effective teacher professional development for English language learners.