Not less than one hour of each school week shall be devoted to the study of the subject mentioned in Section 27-3 in the seventh and eighth grades or their equivalent, and not less than one hour of each school week to the advanced study thereof in all high school grades, in the public schools and other institutions mentioned in such Section.
This Section does not prevent the study of such subjects in any of the lower grades in such schools or institutions.
105 ILCS 5/27-4