The implementation of a new mathematics syllabus in the elementary context is problematic, especially if it contains a new content area. A professional development model, Transformative Teaching in the Early Years Mathematics (TTEYM) was specifically developed to support the implementation of the new Patterns and Algebra strand. The model was grounded in theories related to a community of practice (Lave & Wenger, 1991), a socio-constructivist perspective (Vygotsky,1962/1934) and effective models of professional development (Clarke & Hollingsworth, 2002; Guskey, 1986). This paper focuses on the effectiveness of the model as six Year 1 teachers worked in pairs developing and implementing learning experiences for three differing aspects of the Patterns and Algebra strand. The results indicate the model offered positive professional learning experiences for the six teachers and assisted them in becoming experts in their own right, especially with regard to content and pedagogical knowledge of the Patterns and Algebra strand. (Contains 3 figures.)