The board shall set the definition of a "school day"

The minimum length of the school day shall be seven (7) hours total for all grades, except kindergarten, which shall be five (5) hours. Modification resulting in a school day of less than the above-specified length must be approved by the Board.

All teachers shall be on duty at least seven and one-half (7 1/2) hours and such additional time as the administrative organization requires.