Unfortunately it looks like the education is really old fashioned
Apart from math, there seems to be only very questionable natural science material and very little of that. Modern literature of course is absent. Most of this of course only gets important in the higher grades.
There are some projects for free text-books, but I remember at the moment only
https://openstaxcollege.org/books and that is unfortunately for university level, but I guess there are other projects like that for school grades.