Possession of alcoholic beverages on the grounds of a public school

(a) Except as provided in subsection (b) of this Code section, no person shall possess any alcoholic beverages upon the grounds or within any structure of a public elementary school; public high school; or public trade, vocational, or industrial school. (b) Subsection (a) of this Code section shall not apply to any situation where alcoholic beverages are used by a teacher for educational purposes nor to any situation where alcoholic beverages are used in a religious ceremony or observance.