School has become a high-stakes environment for K-12 English language learners (ELLs) who are increasingly taught in mainstream classes where they are expected to meet grade-appropriate standards developed for fluent English speakers and where they must demonstrate achievement through standardized tests in English. The mainstreaming of ELLs, along with developments in the field of English as a second language (ESL) itself, such as the integration of language and content teaching, have contributed to the diffusion and devaluation of ESL teacher expertise in the United States. Using Florida as a focal case, we describe the implementation of recent educational policy and the consequences for many ELLs and their teachers. In this context, we overview three separate studies of Florida educators (experienced inservice teachers with ESL expertise, preservice elementary teacher candidates, and preservice secondary English teacher candidates) who are enrolled in teacher education programs designed to "infuse" ESL teacher competencies throughout the general curriculum. We argue that despite the progressive pedagogy and inclusive rhetoric, ELLs continue to be marginalized in mainstream contexts and ESL teacher expertise has been reconstructed as a set of generic good teaching practices appropriate for a broad range of diverse learners. (Contains 4 notes.)