Each teacher employed by the board of education of a school district or a governing board of an educational service center shall be granted at least thirty minutes for lunch each school day, during which time the teacher shall not be required to perform any school activity; except that in a one-teacher school where enforcement of the foregoing provisions may work a hardship, the governing board of the service center in which the one-teacher school is located may require the teacher to remain on duty.
The granting of the lunch period to a teacher shall not be cause for lengthening the school day.