Don't know why you're being downvoted as the role of educational companies seems to be pretty large in the standardization and homogenization of schools and curriculums. Compared to the large publishers most school districts are pretty small fish- they don't have time to ensure compliance with all the regulations and standards, so their only choice is to buy a curriculum from a publisher. And of course buying a curriculum is not a one time expense- it's all licensed/subscription based and basically a direct pipeline from local taxpayers' pockets to large corporate publishers.