Christian Christrup Kjeldsen, kjeldsen@edu.au.dk This study investigates the potential of integrating International Large-Scale Assessment (ILSA) data, including PISA, TIMSS, and PIRLS, with Denmark's Educational Management Information Systems (EMIS), particularly the Teacher-Student Register for Primary and Lower Secondary Education, maintained by Statistics Denmark (DST). The research evaluates the availability and legal frameworks surrounding the use of these data and explores existing academic projects leveraging this integration. Denmark's EMIS includes longitudinal, detailed datasets on students, teachers, and classrooms, linked via the unique Central Person Register (CPR) number, a personal identifier assigned to all residents. This system enables the secure linkage of education, socioeconomic, and demographic data, offering comprehensive insights into educational trends. However, access to these data is strictly regulated, requiring adherence to privacy laws and DST’s application process. The Danish contribution examines how these integrated data systems are utilized within the academic community, particularly focusing on the reliability of traditional socioeconomic scales from ILSA surveys (e.g., parental education, occupation) versus administrative indicators such as parental income and employment. Using Denmark's EMIS, the research also evaluates the evolving role of "books at home" as a proxy for socioeconomic status (SES) and its correlation with academic achievement. By combining ILSA data with Denmark's EMIS, the study contributes to the discourse on leveraging administrative data for longitudinal research. It demonstrates the value of integrating survey data with national registers, offering actionable insights into the dynamics of socioeconomic factors and educational outcomes. These findings underscore the need for improved data access and methodological innovations to enhance the use of EMIS in international educational research.

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