Challenging behaviors are one of the most common concerns of early educators, and preschool teachers continue to report feeling unprepared to meet the needs of children displaying challenging behaviors. Overall, traditional standardized classroom assessments have evaluated global classroom quality, but they may not capture the reciprocal and recursive nature of interactions present in preschool classrooms in a manner that can be easily quantified. The current investigation presents initial psychometric information for the Student Behavior Teacher Response (SBTR) observation scheme, a measure that captures instances of challenging behavior and the teacher's response to the behavior. In a sample of 88 Head Start teachers, the observation system exhibited preliminary evidence of inter-rater score agreement and reliability, as well as convergent and discriminant validity. Implications for educators and early childhood assessments are discussed. (author abstract)