Del. Code tit. 14, § 2105

When any bonds shall be sold and delivered pursuant to this chapter, the certification by the Department of Elections conducting the election pursuant to § 1083(d)(2) of this title and the certification by the school board of the district issuing such bonds that the bonds have been issued in due compliance with this chapter shall be conclusive upon the district and all and every other person whatsoever of the right, power and authority for the issuance of said bonds and the legality and validity thereof and of the principal debt and interest represented thereby, and the legality and validity of such bonds shall thereafter not be subject to question in any court by the district or by any person for or on its behalf, and this provision shall be and become part of the contract and obligation represented by each such bond.