Khan Academy
Khan Academy is a nonprofit, founded in 2008 by Sal Khan, that offers free online learning across mathematics, science, economics, computing, and the arts and humanities, spanning kindergarten through early college. It is best understood as curriculum-aligned content rather than a bare standards framework: the material is organised into a subject-to-skill knowledge tree, where each course breaks into units, skills and mastery levels, so a learner (or an AI tutor) can move through a graded progression instead of a flat pile of lessons. Each skill combines short instructional videos, written articles and interactive exercises, and progress is tracked against a mastery model that decides when a concept is learned before the learner advances.
For a builder, the honest constraint is access. Khan Academy retired its public REST API, and the newer internal GraphQL endpoint blocks external requests, so there is no supported route to pull the catalogue as bulk data. In practice you read it on the site, and any ingestion means parsing rendered pages, which limits how cleanly you can turn it into retrieval passages. The written articles chunk reasonably by heading, while video content is transcript-dependent and harder to treat as text.
Where it earns its place is the structure. The ordered skill tree is a useful spine for an AI tutor that needs to sequence teaching by subject and level, and the articles ground plain, school-level explanations.
The licence is the caveat to read carefully. Content is released under Creative Commons Attribution-NonCommercial-ShareAlike 4.0, so use is free but strictly non-commercial, adaptations must carry the same licence, and attribution to Khan Academy with a link is required. Video licensing has been reported to differ from the articles and exercises, so confirm per item. Commercial builders should treat it like the non-commercial OER we list (parts of LibreTexts and OER Commons) rather than the commercially clean OpenStax and MIT OpenCourseWare.
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.
LibreTexts
One of the largest open textbook platforms, covering higher education with some K-12 material. Hosts interlinked textbooks and reference material across science, mathematics, humanities, and social sciences. Mostly NonCommercial, so commercial use is ruled out.