In all cases in which, before the effective date of this Act, the superintendent of the educational service region of the region containing all of the territory proposed to be organized and established into a community unit school district, or a greater per cent of the assessed valuation of the proposed district than is contained in any other region in which assessed valuation of the proposed district is situated, has called an election for the purpose of submitting to the electors of the compact and contiguous territory proposed to be organized and established into a community unit school district the proposition of establishing that territory into a community unit school district, and a majority of those electors voting on the proposition has voted in favor of the proposition of establishing the territory into a community unit school district, and in which at a subsequent election similarly called and held a board of education has been chosen for such district, each such election is hereby made legal and valid and such territory is hereby declared legally and validly organized and established as a community unit school district, and a valid and existing school district.