This article examines the language proficiency and achievement outcomes of Latino students enrolled in a dual language programme who varied by language proficiency (Native English speakers, Current English Language Learners--ELLs, Fluent English Proficient/Previous ELLs). Most previous research has not disaggregated Latino students, especially ELLs. The purpose of this research is to examine the achievement and language proficiency of 732 Grade 4 to Grade 8 Latino students enrolled in a dual language programme who differed by language proficiency. Results show that these Latino student groups achieve at higher levels than their peers in English mainstream. Findings also indicated that the three groups vary in parent education, language proficiency in Spanish, and achievement as measured in Spanish and English. Further, Fluent English Proficient/Previous ELLs are the most Spanish proficient and bilingual, achieve at higher levels in English and Spanish, and close the achievement gap with native English speakers in English mainstream programmes. (Contains 7 tables.)