Peter HughesDerived initially from the observation of children’s methods of counting, Mathematics Recovery and Count Me in Too, the New Zealand Numeracy Projects have, as a starting point for the training of teachers, the understanding and use of a strategy framework that traces children’s development in number reasoning. Research indicated the usefulness of teachers interviewing students in their own class, and viewing video clips of strategic reasoning across of a wide range of ages of student. This paper outlines how interviews and the video clips are incorporated into the initial stages of teacher Professional Development in learning to use the strategy number framework.