Wikiversity
Wikiversity is a Wikimedia Foundation project that hosts free, collaboratively written learning materials: lessons, courses, tutorials, reading guides and self-study projects, organised by subject and by educational level from primary through to tertiary and informal adult learning. It launched in 2006 and runs as separate language editions (English plus around ten others), with content grouped under broad portals such as physical sciences, life sciences, engineering and technology, humanities, social sciences and professional schools. It is not a formal curriculum framework: there is no official, ordered set of national standards or graded competencies. It is curriculum-aligned content, graded teaching material contributed by volunteers, so coverage and depth vary by topic and the sequencing is looser than a published textbook.
You access it the same way as the other Wikimedia projects. Full database dumps are published at dumps.wikimedia.org, there is a MediaWiki API and a Special Export tool for pulling individual pages, and any page can be read as HTML or exported as PDF. For a RAG pipeline the practical route is to take the dump or API output, strip the wikitext markup as you would for Wikipedia, and chunk on the existing section headings, keeping lesson and quiz pages as self-contained passages. That makes it useful for AI tutors that need to sequence explanations by subject and level, and for study-support tools that want worked lessons rather than encyclopaedic prose.
The licence position is favourable for builders. Text is released under Creative Commons Attribution ShareAlike (CC BY-SA 4.0), with some older or imported content also under the GFDL. Commercial use is permitted, but you must credit the contributors and release any derived text under the same share-alike terms, and embedded media may carry different licences, so check before redistributing. Alongside the more structured OER we list (OpenStax, MIT OpenCourseWare, LibreTexts, OER Commons and MERLOT), Wikiversity fills the gap for informal, community-written lessons across a very wide range of subjects.
Related sources
CASE Network (1EdTech)
A public registry of machine-readable learning-standard frameworks from all 50 US states and other issuing agencies, run by 1EdTech in the CASE JSON format. The digitally referenceable spine of what to teach, at which level and in what order, rather than the teaching content itself.
CK-12 Foundation
Free K-12 library of customisable FlexBook textbooks, strong in maths and science, with adaptive practice, interactive simulations and study guides, organised by grade level and aligned to state standards. Non-commercial licence.
Common Core State Standards
The US Common Core State Standards for English language arts and mathematics, defined grade by grade from kindergarten to grade twelve. A widely adopted curriculum framework, available in machine-readable form through ASN and CASE.
Khan Academy
A free nonprofit learning platform organised as a subject-to-skill knowledge tree across maths, science, economics and the humanities, from primary through early college. Videos, articles and mastery-based exercises, but non-commercial licensing and no public data API.