Elementary school districts shall give instruction only to pupils in grades one (1) through eight (8), and may give instruction in kindergarten. All other school districts shall give instruction to pupils in grades one (1) through twelve (12), and may give instruction in kindergarten, and shall maintain secondary schools giving instruction to pupils in grades seven (7) through twelve (12), or any combination of such grades.
Any school district maintaining its only secondary school building situate not less than twenty-five (25) miles from the nearest Idaho secondary school, and which employs not less than six (6) teachers within its district, may be authorized by the state board of education to instruct pupils in two (2) or more grades above grade seven (7).
Whenever any district lies, or shall lie, in more than one (1) county it shall be designated as a joint district of its class.