It is thought that gains in student learning from the use of digital technologies are more likely to be related to teachers' practice than the technology itself. In secondary schooling, a key aspect of this is concerned with understanding how digital technologies are used to support teaching and learning in specific subject areas. Subject areas have their own conventions and expectations for learning that will influence teachers' technology use and technology-supported student tasks. The aim of this paper is to present confirmatory factor analysis of a scale considering common technology-related tasks in three subject areas. Data included in the current analysis are teacher questionnaires collected in 2010 (N = 3624), as part of a large-scale one-to-one laptop initiative in Australia. Results from the 2010 data confirm a five-factor structure revealing significant differences in teachers' professional and instructional uses of digital technologies among three core subject areas: English, Mathematics and Science. Trends are confirmed through a second teacher data set collected in 2011 for Wave 2 of the same one-on-one laptop initiative. Implications of these findings in relation to understanding and supporting effective technology integration and areas of future research are discussed.