Parents value it as a genuinely free, decent-quality textbook library, especially for middle and high school biology, chemistry and physics, and for dyslexic students who use the read-aloud support. It is not a daily curriculum: there is no schedule or lesson plan, and many families pair it with another program or use it only to fill gaps. The main criticisms are uneven quality between books and that, without structure, it often goes unused.
Parents love
Completely free, no paid tier
Interactive simulations for hard concepts
Audio support helps struggling readers
Common complaints
No lesson plans or daily schedule
Quality varies from book to book
Not built for K–2 or hands-on labs
Who it fits
Best for
No religious content. Secular, standards-aligned textbooks
Textbook + labs. Digital textbooks are the core
Online. Runs online
Video lessons a big plus. Videos are embedded in the FlexBooks
Video lessons nice to have. Videos are embedded in the FlexBooks
Minimal: solo work. Self-directed teens can work alone
Some: 20–30 min daily. Parent sets the schedule and checks in
Rusty. Lessons teach the concepts for you
I'd rather a video or script teach. Video or the program does the teaching
Traditional. Textbook, practice and quizzes
Eclectic. Free to mix into any plan
Less suited for
Christian, young-earth creation. Teaches evolution and an old earth
Mostly offline. Screen-based
These come straight from the scoring rules the quiz uses.
Similar programs
Generation GeniusShort, polished NGSS science videos for K–8 with lesson plans, quizzes and DIY activities
Mystery ScienceQuestion-driven K–5 video lessons, each paired with a hands-on activity using household items
MEL ScienceMonthly real-chemistry and physics experiment kits with app, video guides and VR
Questions parents ask
Is CK-12 Foundation Science a full science curriculum?
No. We list CK-12 Foundation Science as a supplement: it's enrichment to use alongside a core program, not a full science curriculum on its own.
How does CK-12 Foundation Science teach science?
CK-12 Foundation Science is described as online textbooks with videos, interactive simulations and practice. Parent prep: moderate (free, but parent must choose books and set the schedule).
What grades does CK-12 Foundation Science cover?
CK-12 Foundation Science covers grades 3rd–12th.
How much does CK-12 Foundation Science cost?
Free; nonprofit with no paid tier.
Is CK-12 Foundation Science creationist or secular?
No religious content; teaches evolution.
Is CK-12 Foundation Science online?
Online. The program does the teaching.
Does CK-12 Foundation Science have a placement test?
No. Pick the FlexBook for your child's grade and subject