Between all those there might be some decent open source education. The problem is that most of the information on the internet is written for adults, so it would be difficult to find one big 4th grade science curriculum in one place. Then there all the quizzes, pictures and vocab people expect in a textbook.
So we have a grandiose task on our hands. Do we A. Buy up the copyright to a series of defunct textbooks, and put them up on an editable wiki. (I'm completely uninformed about the cost and difficulty of this. or B: Create texts from scratch following a standard school textbook model, or C: Some unforeseen option.
It'll take planning and resources, but people thought a moneybomb was a crazy idea at one point.