Development of a Teacher of Mathematics Identity (ToMI) Scale

A measure of teacher identity specific to teachers of mathematics was developed and assessed, the teacher of mathematics identity (ToMI) scale. A sample of teachers was recruited from a state-based mathematics association to complete an online survey including items based on the theories of Mead, Erikson, and Wenger. The subscales of belonging to a mathematics community, self-efficacy as a teacher of mathematics, and enthusiasm to be a teacher of mathematics were derived using exploratory factor analysis (n = 301) and then confirmed with confirmatory factor analysis (n = 311) with randomly allocated independent subsamples. These subscales were related and, when combined to form a single factor, explained a substantial proportion of the variance in the data, suggesting that the ToMI scale can be used as three separate subscales or combined to form a single overarching construct. Overall, ToMI and subscale scores were used in the validation process. Tests of validity were run in the two randomly allocated subsamples independently, allowing for replication of findings. As predicted based on the literature, the ToMI scale and subscales were related to the number of years teaching mathematics, the size of teacher of mathematics network accessed by teachers, and participation in mathematics-specific self-directed professional learning and wellbeing while teaching mathematics. These results reveal this initial iteration of the ToMI scale as valid concerning the underlying teacher identity theory, providing an important research avenue to pursue our understanding and development of effective teachers of mathematics.