Whenever any school district acquires a site for a school building in advance of its need and in accordance with a long range master plan for school building construction approved by the Department of Education to the extent that the cost of the acquisition shall be deemed reasonable by the Department of Education, the Commonwealth shall pay, in the year of such acquisition, one hundred percent (100%) of the reimbursement due the district under applicable laws in force at that time for the cost of acquisition. If such site is not thereafter used by the district for school building purposes, within a period of ten years from date of purchase, the amounts paid to the district under this section shall be returned to the Commonwealth by the district within two years of the end of such ten year period of non-user. If such amounts are not so returned within such two year period, Commonwealth moneys due and payable to the district by the Department of Education as a subsidy or reimbursement for any purpose shall first be withheld in the amount of the moneys owed the Commonwealth by the district under this section and credited as returned in full hereunder before any part of such Commonwealth reimbursement or subsidy is paid to the district. The district shall not be required to return the funds it received if the district can demonstrate in its long range plan that the site will still be needed for a school building, even though the site may be used temporarily by a political subdivision, or agency thereof, for public purposes. If the district conveys or transfers the site to another party, the district shall repay the amount it was reimbursed and appropriate interest, as determined by the department.