It is not lawful for any person who is less than five or more than twenty-one years of age to attend any of the public schools of this State, including kindergarten, except that:

(1) Persons over twenty-one years of age may attend night schools;

(2) When a pupil is in the graduating class and becomes twenty-one years of age before graduation, he is permitted to complete the term if otherwise qualified to do so;

(3) Students may enter kindergarten in the public schools of this State if they will attain the age of five on or before September first of the applicable school year or have substantially initiated a public school kindergarten program in another state that has a different attendance age requirement from South Carolina;

(4) Students may not enter the first grade in the public schools of this State unless they will attain the age of six on or before September first of the applicable school year or have substantially initiated a first grade program in another state that has a different attendance age requirement from South Carolina or have attended a public school kindergarten program for one full school year;

(5) The restrictions in this section may be waived by the local board of school trustees in any proper case. However, that if the provisions of items (3) and (4) of this section are not complied with, the school district is not entitled to receive any state aid for any students who fail to meet these requirements;

(6) Four-year-olds may attend optional child development programs and all three-year-old, four-year-old, and five-year-old children with disabilities in accordance with their individual education program, may participate in any public education preschool program, including optional child development programs. Children with disabilities served in four-year-old optional child development programs may be counted for funding under both funding sources.