A Kindergarten Unit: Cardinality

This paper addresses the learning trajectory used in developing students’ sense of cardinality and how this trajectory aids teachers in advancing students through their developmental progression of number sense. This paper also delineates the crucial aspect of subitizing in addition to one-to-one correspondence as viable methods for determining cardinality. An argument is made for the inclusion of subitizing into the learning trajectory and the Common Core State Standards. The use of manipulatives in teaching cardinality and misconceptions are also examined. The instructional framework known as Problem-Based Learning is discussed, and it is used in creating three cardinality lessons that correspond with the learning trajectory for cardinality and the Common Core State Standards.