Selective mutism (SM) is a childhood disorder characterized by failure to speak in social situations, despite there being an expectation to speak and the capacity to do so. There has been a focus on elucidating the differences between SM and anxiety disorder (ANX) in the recent literature. Although children with SM exhibit more symptoms at school than at home, the assessment of SM typically does not involve teacher reports. There is also a lack of research to help us better understand how to best support students with SM in the classroom, and linking assessment to intervention. The "Teacher Telephone Interview: Selective Mutism and Anxiety in the School Setting" (TTI-SM) was developed by a group of researchers across three large children's hospitals in Canada, within specialized ANXs Clinics, with the goal of addressing several of these diagnostic and treatment issues. Child participants (ages 6-11) were referred for SM (n = 19) or ANX (n = 10). Findings revealed that the SM subscale of the TTI-SM has acceptable psychometric properties. Scores on the SM subscale between the two groups of children were statistically significant t(29) = -3.67, p < 0.001, ?[superscript2] = 0.33, suggesting that the SM subscale was able to distinguish between children with SM and ANX. Given the promising findings, and possible uses of this tool for assessment and intervention, the TTI-SM warrants further research. The role of the teacher in the assessment of children with SM and anxiety disorders, and future directions are discussed.