05- 071 C.M.R. ch. 124, § 5
A school administrative unit shall make provision for the maintenance of all its schools for at least 180 school days. At least 175 school days shall be used for instruction. In meeting the requirement of a 180-day school year, no more than 5 days may be used for in-service education for teachers, administrative meetings, parent-teacher conferences, records' days and similar activities.
Instructional time for public preschool program shall be a minimum of 10 hours per week for 35 weeks and shall not include rest time. Public preschool programs shall schedule within the 175 school days that the school administrative unit has designated as instructional time, but does not have to use all days, allowing flexibility as to numbers of days per week.
Extended public preschool program Day: A school administrative unit is encouraged to schedule public preschool for more than 10 hours per week to improve child outcomes and to reduce the risk of later school failure.
05- 071 C.M.R. ch. 124, § 5