This paper explores teachers' understanding of subject-area knowledge practices (e.g. curriculum, goals, and pedagogy of a subject area, etc.) and technology integration, through the use of Legitimation Code Theory. Drawing on a major study of a technological initiative in all state secondary schools in New South Wales, Australia, this paper illustratively uses one dimension of LCT to explore the organising principles underlying the key subjects of Mathematics and English, in relation to teachers' perceptions of technology use in learning and teaching. Analysis suggests a 'code clash' with Mathematics and a 'code match' with English might help explain their different patterns of integration of ICTs. The research is novel and innovative in both its use of theory and combining the separate fields of educational technology and sociology of knowledge.