Mo. Rev. Stat. § 160.041 – Minimum school day, school month, school year, defined — reduction of required number of hours and days, when

1. The "minimum school day" consists of three hours in which the pupils are under the guidance and direction of teachers in the teaching process. A "school month" consists of four weeks of five days each. The "school year" commences on the first day of July and ends on the thirtieth day of June following.
2. Notwithstanding the provisions of subsection 1 of this section, the commissioner of education is authorized to reduce the required number of hours and days in which the pupils are under the guidance and direction of teachers in the teaching process if:
1. (1) There is damage to or destruction of a public school facility which requires the dual utilization of another school facility; or
2. (2) Flooding or other inclement weather as defined in subsection 1 of section 171.033, RSMo, prevents students from attending the public school facility.
  Such reduction shall not extend beyond two calendar years in duration.

(L. 1963 p. 200 § 1-4, A.L. 1977 H.B. 130, A.L. 1982 S.B. 832, A.L. 1983 S.B. 39, A.L. 1984 H.B. 1456 & 1197, A.L. 1993 S.B. 380, A.L. 1994 S.B. 442, A.L. 2007 S.B. 64)

(Source: RSMo 1959 § 163.020)

CROSS REFERENCE:

Make-up days required due to cancellation for inclement weather, RSMo 171.033