§ 3029. Hours of continuous duty for full time teachers. Except in a city having a population of one million or more persons the school authorities of any school district employing two or more teachers shall fix the hours of duty for full time teachers so that no teacher shall be assigned continuous duty for a length of time in excess of five hours. When the daily total hours of duty exceed five, duties must be assigned so as to provide a period of at least thirty minutes in length which shall be free from assigned duties and which shall be scheduled so far as practical during the hours normally allotted for pupils' lunch periods.