For the purpose of § 22.1-271.2: “Admit” or “admission” means the official enrollment or reenrollment for attendance at any grade level, whether full-time or part-time, of any student by any school. “Admitting official” means the school principal or his designated representative if a public school; if a nonpublic school or child-care center, the principal, headmaster or director of the school or center. “Documentary proof” means written certification that a student has been immunized, such certificate to be on a form provided by the State Department of Health and signed by the licensed immunizing physician or an employee of the immunizing local health department. “Student” means any person who seeks admission to a school, or for whom admission to a school is sought by a parent or guardian, and who will not have attained the age of 20 years by the start of the school term for which admission is sought. “Immunized” or “immunization” means initial immunization and any boosters or reimmunizations required by § 32.1-46. “School” means (i) any public school from kindergarten through grade 12 operated under the authority of any locality within the Commonwealth, (ii) any private or religious school that offers instruction at any level or grade from kindergarten through grade twelve, and (iii) any private or religious nursery school or preschool, or any private or religious child-care center required to be licensed by the Commonwealth.