In the absence of express contract, a session of 3 hours in the forenoon and 3 hours in the afternoon shall constitute a school day, 5 such days a school week, and 4 such weeks a school month, in the public schools.
RSA 189:40
1883, 33:1. PS 92:20. 1921, 85, II:21. PL 117 :36. RL 135:40.