No action shall be brought questioning the legality of the organization, reorganization, enlargement, or change in the boundaries of any school corporation in this state unless brought within six months after the date of the filing of said written description in the office of said county auditor or county auditors. When the said period of limitations shall have passed, it shall be conclusively presumed that all acts and proceedings taken with reference to the said organization, reorganization, enlargement or change in boundaries were legally taken for every purpose whatsoever and that a de jure school corporation exists.
Iowa Code § 274.5