As a young teacher-leader, Heidi encountered the power of teachers learning together to improve student achievement; over five years, she and her 16 colleagues raised scores 30 percentage points, from 10 points below the state average to 10 above. In that experience, the team proved true their theory of action—if students are empowered to collaboratively solve rich mathematics problems, they will develop perseverance and understanding, resulting in increased achievement. Those early years shaped Heidi’s deep respect for the professionalism of teachers and the necessity of building a shared vision of excellent pedagogy. She has shared this passion with others through designing and leading professional development in math pedagogy and leadership across schools in the US and worldwide.