(a) The use of tobacco products in any school building is hereby prohibited. No board of education of any school district shall allow any person to use tobacco products in any school building.

(b) As used in this section, the term “school building” means any enclosed building used for pupil attendance purposes by the board of education of a unified school district. The term school building does not include a building, or part thereof, used for residential purposes or leased from the school district for nonschool sponsored activities.