This article presents a descriptive, critical analysis of the comparability of information concerning students, teachers, and school resources gathered by organisations within government jurisdiction, and the pitfalls for the unwary researcher using government data banks. Differences in the method of compiling information about citizens, and changes over time from basic census information to sophisticated national and international school comparison are referenced. An under-standing of the development of education data collection by governments is useful for researchers accessing government data sources. Researchers are limited in data analysis according to the comparability of data, and the structure and characteristics of a particular data bank may preclude comparison. Risks for education researchers who make use of information from large government data banks for their particular research focus are identified and illuminated. Problems concerning data gathering under the Australian federated education system are illustrated and inconsistencies revealed in order to alert researchers to the need to question more critically the comparability of the data they intend to use.