Whenever any board of school directors of any school district shall have heretofore contracted for labor, materials and supplies for the school district, the purchase of which by contract is authorized under the provisions of the school laws of the Commonwealth, and such board of school directors has actually received such labor, materials and supplies and the same are being used by the school district, if the said contract does not evidence any fraud or conspiracy to violate the provisions of the school laws of the Commonwealth and the school district has not suffered any pecuniary loss as the result of such contract, then such contract shall be valid and binding on the school district and payment for such labor, materials and supplies by the school district is hereby authorized, ratified, confirmed and validated, notwithstanding the fact that such contract was legally null and void by reason of the failure to advertise for bids or by reason of defect in the advertising or by reason of any other defect in compliance with or in the failure or omission to comply with the school laws of this Commonwealth regulating the award of contracts for such labor, materials and supplies. No board of school directors nor any members thereof shall be subject to surcharge for payments made by any board of school directors on any such contract.