The Green School uses Investigations in Number, Data, and Space in teaching mathematics. This complete K-5 program, developed by TERC to correlate to the NCTM Standards, focuses on the major strands of mathematics: number, geometry and measurement, data analysis, and the mathematics of change. The investigations in the curriculum have been designed to engage students in key mathematical contexts as they develop number sense, learn to visualize and describe geometric relationships, and collect and analyze real data. Students work together to explore mathematical problems in depth, use a variety of materials and technology, and express their mathematical thinking through talking, drawing, and writing .