Within the Australian education system, Aboriginal students' use of non-standard English features is often viewed simplistically as evidence of non-attainment of literacy and oral-English milestones. One reason for this is the widespread use of assessment tools which fail to differentiate between native-English speakers and students who are learning English as a second language. In these assessments, non-standard English features are framed as "mistakes" and low scores taken as evidence of "poor" performance. This paper will contrast a mistake-oriented analysis with one that incorporates knowledge of the students' first language. It will clearly show that when consideration is given to the first language, a more nuanced picture of English proficiency emerges: one that is attuned to the specific second language learning pathway and thus far better placed to inform both assessment and classroom instruction.