This study explores the private theories of four vocational education teachers in Singapore who have engaged in the design of technology-based learning for their own classes. The understanding of teachers' private theories is important in the context of contemporary educational reforms, which emphasise the shift towards student-centred practices and technology integration. As teachers learn to change strategies and utilise technology, they might also need to transform aspects of their private theories that could impede effective technology integration and lead them to continue with outdated educational practice. This study aims to understand and explicate areas of private theories that impede the effective design of student-centred technology-based learning. The final outcome of the study was a set of propositions for readers to examine for the possible application in their own environments.