The assessment of sign language proficiency is essential for evaluating the outcomes of sign bilingual education. This paper reports an attempt to assess the sign language proficiency of children in a self-described sign bilingual program in Sydney by adapting a British Sign Language (BSL) test to Australian Sign Language (Auslan). The test appears to measure basic Auslan skills in young children and, in particular, appears to identify native-like signers. However, two qualifications need to be made regarding how standardized norms are established (and thus their interpretation) and the make-up and population size of this study. Namely, the original BSL test is not normed on native signers alone; and the number of subjects in the study is extremely small and varied. These factors limit the generalizations that can be made from the data. Further testing with a larger population of signers is essential before results could be confidently interpreted. However, due to the small number of potential subjects in Australia, such data may never become available. Despite these observations and qualifications, it does appear from this study that the sign bilingual program under investigation faces important challenges in ensuring that all children achieve early native-like proficiency in the community signed language.