The enduring monolingual mindset in English-speaking countries results in widespread belief that additional language learning takes time away from literacy in the societal language. Yet, extensive research has shown that time spent learning additional languages enhances learners' literacy skills, providing first language literacy is sufficiently supported. This paper examines the achievements of students at four primary schools in Australia, where bilingual programmes were implemented to teach subject content through an additional language. Data from the national standardised literacy and numeracy assessment were gathered to compare students within the bilingual programmes with those not in the bilingual programmes. Results show higher performance for students in the bilingual programmes compared to their peers in monolingual classes. Drawing on data from a broader study of formal and informal assessment in these schools, this paper presents the standardised test results and teacher qualitative beliefs about literacy development. Findings show that the bilingual style of learning suits children irrespective of many contextual factors and that children's literacy in English is enhanced by the addition of a second or subsequent language.