Dual immersion schools in the United States, which combine native Spanish speakers and students learning Spanish as an L2, encourage English development while promoting Spanish learning. However, relatively little is known about the levels of Spanish attained by dual immersion graduates. This case study describes the performance on a number of measures of a graduating class at a Spanish-English dual immersion school. It analyzes their proficiency in speaking, reading and writing, their production of three grammatical forms, and their ability to identify and produce appropriately polite Spanish. Heritage Spanish speakers evidenced fairly strong Spanish systems. L2 Spanish learners scored low on several measures, but overall could communicate their ideas. Several recommendations are offered for immersion classroom pedagogy.