§ 3622. Routes. The board of education or trustees shall plan each school transportation route, as defined in subdivision three of section thirty-six hundred twenty-one of this article, in such manner as to promote maximum efficiency in the operation of a school bus on such route. Whenever practicable each route shall be planned to operate within the boundary of a school district. If any or all pupils of a school district receive instruction in a school or schools beyond the boundary of such district, the board shall plan a route or routes beyond the boundary of such district to such school or schools for such pupils.