Minn. Stat. § 120A.415: EXTENDED SCHOOL CALENDAR.

A school board that offers licensed kindergarten through grade 12 teachers the opportunity for more staff development training and additional salary under section 122A.40, subdivisions 7 and 7a, or 122A.41, subdivisions 4 and 4a, must adopt as its school calendar a total of 240 days of student instruction and staff development, of which the total number of staff development days equals the difference between the total number of days of student instruction and 240 days. A school board may schedule additional staff development days throughout the calendar year.