(a) Except as provided under subsection (b) of this section, a driver of a motor vehicle shall not use a handheld wireless telephone while operating a motor vehicle when passing a school building or school zone during school hours when children are present and outside the building.
(b) A driver of a motor vehicle who is passing a school building or school zone during school hours when children are present and outside the building may use a handheld wireless telephone while operating a motor vehicle for an emergency purpose.
(c) This section does not apply to law enforcement officers.