Free digital textbooks approved by California

Five digital textbooks from CK-12 Foundation have recently met 100% of the California content standards for their respective courses. The foundation provides free, up-to-date, standards-aligned digital textbooks.

The five CK-12 FlexBooks now available for access by California educators at are: CK-12 Probability and Statistics (Basic), CK-12 Probability and Statistics (Advanced), CK-12 Biology I (rev), CK-12 Earth Science (rev), and CK-12 Life Science (rev).

As the Foundation expands the reach of its quality open-source content across the nation, it has been working to align FlexBook content with the standards of many of the 50 states. For more information, visit