Professional organizations in mathematics education have been calling for a greater focus on "Big Ideas" in mathematics for decades. Most recently, the National Council for Teachers of Mathematics (NCTM) wrote the following in their research summary, "Catalyzing Change in High School Mathematics":
It is frequently challenging for high school mathematics teachers to teach at the desired level of rigor—to develop students’ conceptual understanding, procedural fluency, problem-solving skills, and critical thinking skills, while cultivating positive student mathematical identities—given the sheer number of expected learning standards. A focus on a set of Essential Concepts would allow high school mathematics teachers to provide the high-quality instruction that is critical for all students if they are to learn and understand foundational mathematics at a deep level. Knowledge of the Essential Concepts is necessary to open up professional and personal opportunities, as well as to cultivate a rich set of tools that students can use to apply mathematics meaningfully to understand and critique the world that they inhabit.
Using the resources from "Catalyzing Change in High School Mathematics" and from NCTM's "Essential Understanding Series," a team of mathematics teachers from across the district developed the following Essential Concepts in the strands of: 1) Algebra and Functions, 2) Geometry and Measurement, and 3) Statistics and Probability. The Essential Concepts represent the deep understanding that students should develop in their first three years of our program. They guided the development of curricular support materials and can be used by school sites for assessment purposes. These Essential Concepts are meant to be a "living draft," open to revision in response to changes in mathematics education and to changes in the needs of our students.