Effective classroom management is critical for student and teacher success. Because teachers receive limited preservice preparation and in-service support in classroom management, educational leaders (e.g., school psychologists, behavior coaches, mentor teachers, and administrators) need efficient and effective tools to identify teachers' strengths and needs and to guide professional development. Current approaches to assess teachers' classroom management are either (a) simple and efficient, but have unknown psychometric properties, or (b) psychometrically sound, but resource intensive. Thus, a Classroom Management Observation Tool (CMOT) that is simple, efficient, and has promising psychometric properties would fill a critical need in the field. This article describes the initial development and validation of the CMOT-a four-item rating of teachers' active supervision, opportunities to respond, specific praise, and positive to corrective ratio-and presents promising evidence of content validity, factor structure, interrater reliability, construct validity, and generalizability. Further research is needed to develop this tool for screening, progress monitoring, and other assessment purposes. (PsycInfo Database Record (c) 2020 APA, all rights reserved).