If the board of directors shall deem it not to be for the best interests of the district that the lands mentioned in the petition, or some portion thereof, shall be excluded from the district, it shall order that the said petition be denied; but if such board shall deem it to be for the best interests of the district that such lands, or some portion thereof be excluded from the district, and if the secretary of the interior shall in writing give his assent as by this act N.M. Stat. Ann. § 73-8-1 to 73-8-60 hereinbefore provided, then the board may order the lands mentioned in the petition or some portion thereof to be excluded from the district.