Teachers often tend to discuss their English language learners (ELLs) in terms of "level." Writes the author, "But if I were to say to a teacher, 'You have four level 2s in your class,' how does that help us have a common understanding of the students' needs?" One approach that has great potential to increase students' language growth is focusing formative assessment on the specific needs of ELLs. This requires analyzing students' linguistic level and providing specific feedback. To assist them in this work, teachers can use the WIDA Performance Definitions tool for speaking and writing. The tool helps users analyze the academic language skills of an English language learner and provide targeted language feedback according to each of three language dimensions: discourse (linguistic complexity); sentence (language forms and conventions); and word/phrase (vocabulary usage). The author describes what this would look like in a cotaught 2nd grade classroom with 12 English language learners. The 2nd grade teacher and a teacher of English as a second language guide students through a unit on the lifecycle of a butterfly.