Extending the conception of Horizon Content Knowledge: Fundamental mathematical knowledge and a sample assessment item

The purpose of this article is to extend the concept of Horizon Content Knowledge and provide a sample assessment item. Fundamental mathematical knowledge (FMK) is defined as an awareness of the core or in-depth mathematics behind solving a problem. Teachers with fundamental mathematical knowledge can provide students with a more broad and comprehensive approach to solving mathematical problems that extends beyond the rote procedures used to solve a particular problem. We propose that this type of knowledge should be included in the model of Horizon Content Knowledge. Developing items that assess teachers’ Horizon Content Knowledge is worthwhile because this process provides a practical way to illuminate and refine the structure and content of Horizon Content Knowledge.