Educational technology research has been characterised as lacking theoretical frameworks that can enable cumulative knowledge-building across the field. This article explores the value of Legitimation Code Theory (LCT) for addressing these issues by discussing research into the key of integration of information and communication technologies in education. Specifically, it shows how LCT enables the theorisation of knowledge practices, the basis of education but undertheorised by existing research. Drawing on a major study of a technological initiative in all state secondary schools in New South Wales, Australia, the article illustratively uses one dimension of LCT to compare the organising principles underlying the initiative with those underlying the key subjects of mathematics and English. Analysis suggests that a "code clash" with mathematics and a "code match" with English might help explain their different patterns of integration of information and communication technologies. It also demonstrates how LCT can be utilised with multiple methods, enabling the integration of research into a wide range of educational topics and thereby contributing towards building knowledge across the field. (Contains 6 figures and 4 notes.)