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ck12.org

Free Online Textbooks, Flashcards, Adaptive Practice, Real World Examples, Simulations

CK-12 Foundation - Wikipedia

The CK-12 Foundation is a California-based non-profit organization which aims to increase access to low-cost K-12 education in the United States and abroad.[2] CK-12 provides free and customizable K-12 open educational resources aligned to state curriculum standards. As of 2022, the foundation's tools were used by over 200,000,000 students worldwide.

CK-12 was set up to support K-12 Science, Technology, Engineering, and Math (STEM) education.
It first produced content via a web-based platform called "FlexBook."

Team | CK-12 Foundation
with 

Vinod Khosla - Wikipedia
an Indian-American billionaire businessman and venture capitalist. He is a co-founder of Sun Microsystems and the founder of Khosla Ventures

FlexBook - Wikipedia

FlexBook is a textbook authoring platform developed by the CK-12 Foundation launched in 2008, focused on textbooks for the K-12 market. Derived from the words "flexibility" and "textbook," a FlexBook allows users to produce and customize content by re-purposing educational content using different modules.

CK-12 FlexLets | Math & Science Review

EPISD 2019-2020 Economics with Emphasis on the Free Enterprise System | CK-12 Foundation

CK-12 Biology for High School | CK-12 Foundation

World History Studies_EPISD | CK-12 Foundation