All contracts for capital improvements by any school district which are financed in whole or in part with funds received from the state public school building fund pursuant to an application approved by the commission shall be awarded and entered into upon receipt of sealed bids or proposals after the time and place of letting such contracts and the manner of bidding has been duly advertised. The contract shall be let and awarded to the lowest and best bidder but the board of trustees or other governing body of the school district shall have the power to reject any and all bids. No such contract shall be finally awarded or entered into without the prior written approval of the commission. It is hereby expressly provided that in order to bid upon and be awarded contracts for the construction of school facilities under the provisions of this chapter, if such contract, subcontract or undertaking is less than Fifty Thousand Dollars ($50,000.00), it shall not be necessary that the bidder obtain a certificate of responsibility from the Board of Public Contractors under the provisions of Chapter 3, Title 31, of the Mississippi Code of 1972, or otherwise be qualified under said chapter, and none of the provisions of said chapter shall be applicable to such contracts for the construction of school facilities under the provisions hereof. Notwithstanding the foregoing provisions of this section or any other provisions of law, the contract for construction of a secondary vocational and technical training center for exclusive use and operation by a county school district may be entered into and awarded by the board of trustees of a junior college district where a grant of federal funds by the Appalachian Commission has been made to the board of trustees of such junior college district to assist in financing construction of such secondary vocational and technical training facility for such county school district.