Schools play a key role in ensuring that children are being immunized against diseases, but conflicting research is making enforcement difficult. This article discusses a growing trend of vaccine avoidance and the endless supply of conflicting information and research about immunization safety. Despite the controversy, many people appear to accept the health community's assurances that vaccines are safe and beneficial. By and large, the credit for ensuring that most children receive the recommended vaccines before they enter school goes to the states. No federal law requires that children be vaccinated, but all 50 states mandate that children be immunized against a range of infectious diseases such as measles, hepatitis B, pertussis, and tetanus before they enter school. (Contains 1 chart.)