I've wondered why there isn't a set of national texts available for core math and science subjects. They're pretty stable subjects. So at one point I decided to find out what the mission of the Dept. of Education is, and the shocker (to me, at least) was the following little blurb from the ed.gov website.

"In creating the Department of Education, Congress specified that:

No provision of a program administered by the Secretary or by any other officer of the Department shall be construed to authorize the Secretary or any such officer to exercise any direction, supervision, or control over the curriculum, program of instruction, administration, or personnel of any educational institution, school, or school system, over any accrediting agency or association, or over the selection or content of library resources, textbooks, or other instructional materials by any educational institution or school system, except to the extent authorized by law. (Section 103[b], Public Law 96-88)"

So even if we wanted to have national standards for math textbooks, the Dept. of Education is prohibited by law from doing so.