This report discusses the effects of lead exposure and toxicity on children's cognitive development and school performance and addresses the role of schools in prevention of lead poisoning. Sources of lead exposure include mining, smelting and refining activities, lead paint, leaded gasoline, and industrial emissions. The results of lead poisoning are most often dealt with in school systems where, in some cases, over 50 percent of students in special education classes are lead poisoning victims. Although lead can affect every system in the body, the major organ systems affected are the central nervous system, the blood system, and the kidneys. Lead poisoning is manifested in neuropsychological problems, cognitive impairments, and behavior problems. A review of recent studies on children exposed to lead indicates deficiencies in both development and cognitive functioning. Exposure pathways of lead include inhalation of contaminated air and dust and ingestion of contaminated water, food, soil, and dust. The most common source of lead exposure for preschool children is lead-based paint produced before 1940. School systems can play a pro-active role in preventing lead poisoning by identifying and eliminating possible lead hazards in children's homes and in the school environment. In addition to local agencies, federal agencies can assist schools with the prevention of lead poisoning. These include the Centers for Disease Control and Prevention, HUD, National Lead Information Center, National Poison Control Center Hotline, and American Water Works Association. Appendices include a list of the effects of lead poisoning and a summary of studies concerning lead exposure and children. (LP)