Comprehensive school health education (CSHE) can help youth obtain the greatest benefits from education and become healthy and productive adults. One child out of four has an emotional, social, or physical health limitation that interferes with learning. Because schools have the capacity to reach 53 million students every year for 12 years, they are in a unique position to influence young people's physical, mental, and social well-being. Recent reports identify CSHE as a necessary component of a national infrastructure to support children's health. The capacity of CSHE to prevent or eliminate health problems among young people depends on the effectiveness of their teachers. This digest reviews the essential elements of preservice preparation of school-based health educators, focusing on the need for effective, standards-based health education teacher preparation. It describes seven professional standards for the preparation of health education teachers, and it cites research showing that effective curricula implemented by well-prepared teachers can reduce risky behaviors among youth. It concludes that teachers trained according to national standards can have a positive impact on children's health knowledge, skills, and behaviors by effectively delivering CSHE. (Contains 20 references.) (SM)