(a) When any plan of organization of administrative units for a county is found to conform to the standards for approval of administrative units adopted by the State Board of Education, the Department of Public Instruction¹ shall cause such plan to be placed upon the agenda of the Council of Basic Education. The Council of Basic Education shall review all plans placed upon its agenda, and approve such plans as it deems wise in the best interests of the educational system of the Commonwealth. Except as hereinafter provided, no plan of organization of administrative units shall be approved in which any proposed school district contains a pupil population of less than four thousand (4,000), unless when factors of topography, pupil population, community characteristics, transportation of pupils, use of existing school buildings, existing administrative units, potential population changes and the capability of providing a comprehensive program of education are considered by the Council of Basic Education as requiring the approval of a plan of organization of administrative units in which one or more proposed school districts contains a pupil population of less than four thousand (4,000). (b) A plan of organization of administrative units for a county shall be approved by the Council of Basic Education, if the plan contains (i) no unit with a pupil population less than that of the unit with the smallest pupil population in the last previous county-wide plan submitted to and approved by the State Council of Education prior to September 12, 1961, and (ii) no more units than were in the aforesaid county-wide plan plus an additional unit for each second class district which was not required to be a part of such county-wide plan and which was not included in an administrative unit thereof. (c) Pupil population as used in this section shall mean the average daily membership for the school year 1961-1962 including kindergarten or grade one through grade twelve.