In considering achievement difficulties of language minority students, it is important to understand basic concepts about second language acquisition, what it means to be proficient in a language, and how varying levels of language proficiency impact academic performance. Ultimately, language-minority students must develop native-like English conversational and academic language proficiency. Thus, assessment of language skills is one of the cornerstones of instructional planning and of evaluations for the purpose of identifying students who need remedial or special education services. Supporting native language and English acquisition and development is an important aspect of overcoming achievement difficulties.