I would say that the foundation needs some official spot where we could get started on setting up the required teaching material for the educational (and home educational) sector.
My immediate thoughts are that this is mostly a documentation project. It needs to support collaborative writing, translation, peer review, source citations, copyrights and all such stuff. Just like Linux distro documentation efforts? What are the best frameworks out there? I assume the foundation wants to be the 'owner' of the project, as it will become a major part of the future product.
There must be a good framework and a set of clear guidelines/goals. A team of good/engaging writers can then create the main content, and the rest of us can go ahead with supplementary material, graphic layout and translations.
If the Fedora remix is the preferred distro, would there be benefits to adopting the framework used for Fedora documentation? I am not suggesting that the teaching material should be made part of the remix, it should be a separate project.
Engaging the children/students so they become part of the community in the future is equally important. There should be a 'sister-site' for student-driven extensions to the teaching material. A place where children can present their projects and upload texts, source code, pictures, video... This sister site should be child-friendly incorporating google translation facilities.