The San Francisco Unified School District (SFUSD) uses the Language and Literacy Assessment Rubric (LALAR) as the secondary measurement required by the No Child Left Behind (NCLB) Act to measure English proficiency of English language learners (ELLs). In this analysis, the Rasch model is used to identify whether the LALAR is a valid measurement instrument and scale to measure the "English proficiency" of ELLs. This analysis investigates the relationship between student ability (q) and the probability that the student will respond correctly to an item on the LALAR. Controlling for this relationship, the item characteristics of each item, ability of each student, and measurement error associated with each score were mathematically derived. This will allow for validity and reliability tests to be conducted, which will help determine if the LALAR is a useful accountability measure for ELLs.