Implementing best practices like cooperative learning, using concrete manipulatives, problem solving, technology, active learning, multi-age grouping, and team teaching have shown benefits for students when learning mathematics concepts within the curriculum (Zemelman, Daniels & Hyde, 1998; NCTM, 2000). What started as a professional development teacher improvement exercise by a Year 2 and Year 4 teacher has turned into a powerful learning experience for the teachers, students, and the school. Teachers teaching together from different year levels and backgrounds of kids working together are finding great success. This article will explore a lesson on geometry and spatial sense and tessellations which turned into a memorable experience for all the students and teachers. Teachers are beginning to see what really works to get students thinking like mathematicians and enjoying the discipline.