As part of the 'Bridging the Language Gap' project undertaken with 86 State and Catholic schools across Queensland, the language competencies of Indigenous students have been found to be 'invisible' in several key and self-reinforcing ways in school system data. A proliferation of inaccurate, illogical and incomplete data exists about students' home languages and their status as English as an Additional Language/Dialect (EAL/D) learners in schools. This is strongly suggestive of the fact that 'language' is not perceived by school systems as a significant operative variable in student performance, not even in the current education climate of data-driven improvement. Moreover, the National Assessment Program - Literacy and Numeracy (NAPLAN), the annual standardised testing regime, does not collect relevant information on students' language repertoires and levels of proficiency in Standard Australian English (SAE). Indigenous students who are over-represented in NAPLAN under-performance data are targeted through 'Closing the Gap' for interventions to raise their literacy and numeracy achievements (in SAE). However, Indigenous students who are EAL/D learners cannot be disaggregated by system data from their counterparts already fluent in SAE. Reasons behind such profound language invisibility are discussed, as well as the implications for social inclusion of Indigenous students in education.