Objectives: We investigated school factors associated with successful implementation of a seventh grade vaccination requirement.Methods: The proportion of students vaccinated with hepatitis B vaccine and measles containing vaccine was determined from records of schools in San Diego County, California. A school survey identified compliance strategies. Analysis identified factors associated with coverage.Results: In October 1999, 67.2% of 38,875 students had received the required vaccine doses. Of 315 schools, coverage was less than 40% in 60 schools and exceeded 80% in 111 schools. Factors associated with high coverage included private schools, early and frequent notice to parents, and, for public schools, higher overall socioeconomic status of students.Conclusions: In preparation for a middle school vaccination requirement, early and frequent notification of parents improves coverage. Schools with a high percentage of low socioeconomic status students may require extra resources to support implementation. [ABSTRACT FROM AUTHOR]