The professional development school (PDS) can be a catalyst for the professional development of mathematics pre-service as well as in-service teachers. In the present research we describe lower-secondary in-service mathematics teachers' development of ICT integration in their teaching. This is done through the innovation diffusion model, where technology integration in mathematics teaching is considered as an innovation candidate for adoption by mathematics in-service teachers. The research findings indicate that the PDS can support the in-service mathematics teachers in their adoption of new innovations, specifically when this innovation is practiced by the pre-service teachers in the training school.