To those wondering what constitutes as a "school day" on early release days for Iowa:
12.1(9) Minimum school day. A school day shall consist of a minimum of 5½ hours of instructional time for all grades 1 through 12. The minimum hours shall be exclusive of the lunch period. Passing time between classes as well as time spent on parent-teacher conferences may be counted as part of the 5½-hour requirement. The school or school district may record a day of school with less than the minimum instructional hours if emergency health or safety factors require the late arrival or early dismissal of students on a specific day; or if the total hours of instructional time for all grades 1 through 12 in any five consecutive school days equal a minimum of 27½ hours, even though any one day of school is less than the minimum instructional hours because staff development is provided for the instructional professional staff or because parent-teacher conferences have been scheduled beyond the regular school day.