School speed zones are frequently requested as traffic controls for school areas on the basis of the common belief that if a transportation agency would install a reduced speed limit, then drivers would no longer speed through an area. A Texas research project was initiated to review existing practices and to develop guidelines concerning the establishment of school zones. Researchers sought to answer several questions about the relationships between operating speed and reduced-speed school zones. Researchers documented existing knowledge through a review of previous research on the effectiveness of devices, surveys of practitioners and law enforcement officers, and a review of existing school zone guidelines and warrants. In addition, researchers collected speed data at 24 school zones, focusing the analysis on unique characteristics of reduced-speed school zones, such as length, duration, and time of day relative to the start and end of school. Of particular interest was the finding that longer school zones do not result in lower speeds for a longer distance; speeds increased approximately 0.9 mph for every 500 ft of school zone length. Findings from the analysis and discussions with practitioners were used to develop guidelines for traffic control devices, including school speed zones, near schools in Texas. The guidelines were designed to serve as a supplement to the Texas Manual on Uniform Traffic Control Devices and the manual Procedures for Establishing Speed Zones. This paper focuses on the findings from the field studies and presents suggestions concerning school traffic control devices.