This study explores the Spanish proficiency of two groups of home Spanish-speaking students in one Illinois public school: those attending a dual language program (DLP) and those in an English language program (ELP) in the same building. We administered the Language Assessment Scales in Spanish for listening, speaking, reading, writing, and written conventions. The main findings were: (1) Students in the DLP scored higher on all five portions of the Spanish language test than their peers in the ELP; (2) The differences were a good deal larger on production tasks (speaking and writing) than on multiple choice questions (listening comprehension, reading comprehension, and identifying proper written conventions). (3) Overall, home Spanish-speaking students in the ELP evidenced very weak Spanish writing skills in all four grade levels.[KP1] The English scores of the DLP and ELP students in fifth and eighth grade, as measured by two state mandated standardized tests, did not differ to a statistically significant degree. Although this finding does not coincide with plentiful prior research around the country showing that DLP students’ English scores are usually substantially higher than those of their ELP peers, the fact remains that these DLP students’ English scores were not comparatively lower, either. We discuss implications and future directions.