This paper describes a model for teacher professional development as co-design for curriculum planning in which facilitators with design and pedagogical expertise iteratively work with groups of secondary school teachers, one school at a time, to plan whole terms of work, as a form of teacher professional development. It contains preliminary results from a design-based research study involving co-design with digital technologies teachers in two Australian secondary schools. It describes two phases of design involving workshops, strategies and instruments that work to facilitate effective co-design with teachers. Results from this pilot study suggest that the co-design for curriculum planning model leads to high quality teacher professional development for 21st century learning.