Jonathan Katz taught mathematics in New York City for 24 years to a diverse group of students as young as 11 and as old as 19. Over the years his approach to teaching and learning evolved into one that focused on student inquiry and the development of mathematical thinking and understanding. When Jonathan left the classroom to become a mathematics coach and worked with teachers in schools both in NYC and across the country his understanding and thinking about the teaching and learning of mathematics grew enormously. Jonathan’s work today as lead mathematics specialist for the NY Performance Standards Consortium is work that aligns with his deepest beliefs about teaching and learning. “I have come to understand the power and importance of teaching students to think mathematically. It is the means to help students to come to believe in their own capabilities by engaging in mathematical problem solving and do things they never thought possible. Mathematics teaching and learning should be a transformative experience. We can see that happen in the performance based assessment work students are producing.” Jonathan Katz received his doctorate from Teachers College, Columbia University (2009) and has written a book titled, Developing Mathematical Thinking: A Guide to Rethinking the Mathematics Classroom (2014 Rowman & Littlefield).