A systematic review was conducted using PsychInfo, ERIC, and Google Scholar using the terms "classroom" and "direct observation". The search yielded 1,006 articles published between 1935 and 2022 with a total of seven observation codes (Behavioral Observation of Students in Schools, Classroom Observation of Engagement, Disruptive and Disrespectful Behavior, Direct Observation Form, Revised Edition of the School Observation Coding System, Response to Interpersonal and Physically Provoking Situations and the State-Event Classroom Observation System) meeting full inclusion criteria. The current article reviews the structure, content, training requirements and available psychometric evidence of each of the seven aforementioned observation codes. Each observation code was evaluated using criteria for each indicator for psychometric evidence. A synthesis of the reviewed literature indicates the need for increased attention to the psychometric evidence of observation codes, measurement invariance across racial/ethnic groups, and the acceptability of observation methods for school-based practitioners. Recommendations for the use of each observation code based on a synthesis of the reviewed studies and future directions for research in observational assessment are provided.