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CK-12 Foundation
General Summary
- Free, comprehensive online K-12 curriculum with STEM focus
- Interactive lessons combine text, videos, simulations, and practice
- Flexible, adaptive learning with customizable content
- Secular, standards-aligned approach supporting various learning styles
Accessibility: Free Online Learning for Everyone
Parents consistently praise CK-12's open access model that removes financial barriers to quality education:
"What an amazing textbook — for free! I was blown away by how detailed and good this book is." Amazon Review
"Very handy for when you begin homeschooling on a shoestring budget and need up-to-date curriculum." Amazon Review
"CK-12 made it easy for us to avoid those premium products... CK-12 means that the hard work we're doing now is going to last way beyond COVID-19." EdSurge News
STEM Excellence: Strong Math & Science Focus
Families highlight the depth and quality of CK-12's STEM content:
"Math and science is where CK-12 really shines. If your child enjoys CK-12's approach to these subjects, you're in luck, because other subjects from CK-12, including social studies, philosophy and photography, are all available as well." Prodigy
"The material is aligned with state standards and is used by over 200,000,000 students worldwide, so you can rest assured that it is a solid curriculum." Katie Rose Olive
Engaging Format: Interactive & Multi-Modal Learning
Parents appreciate how CK-12's interactive approach keeps students motivated:
"Students enjoy using it because it's a combination of reading and video. Students can also get more engaged using the simulations and PLIX." EdTech Impact Reviews
"I'm still a traditionalist (I love my paper books), but it's nice to have these vivid photos and videos to learn from." Amazon Review
"It uses a variety of methods to teach, catering to a wide variety of learning styles." Katie Rose Olive
Personalized Learning: Adaptive Practice & AI Support
The platform's ability to tailor content to each student receives significant praise:
"CK-12 is adaptive, adjusting questions for your student and introducing new challenges in a personalized, strategic way." Katie Rose Olive
"CK-12 is at the forefront of OER by doing adaptive and personalized learning. More people should be doing it the way they are." David Wiley, Open Education Expert via EdSurge
Parent Involvement: Flexible Support Options
Parents note that CK-12 can work for different levels of oversight:
"I just let my student go through the work and check after. I can look at the assignments before my student completes them and keep up in my copy of the book." Greg, Homeschool Parent via EdTech Impact
"If you have a younger child, the time commitment can feel daunting. Logging them in each day and keeping them engaged can be difficult." Prodigy
User Experience: Navigation & Organization
Some parents mention challenges with the platform's organization:
"The interface can be a little clunky at first. CK-12 may be overwhelming for some families, depending on their homeschool style." Katie Rose Olive
"CK-12 makes assigning mastery-based homework easy... it makes it easy to access free learning resources anywhere." Science Teacher via EdTech Impact
Who Thrives With CK-12?
Well-Suited For:
- Families on a tight budget seeking quality educational content
- Self-motivated students who enjoy interactive and technology-based learning
- Parents who want a flexible curriculum that can be customized
- Visual and hands-on learners who benefit from simulations and interactive exercises
- Students needing a secular, standards-aligned curriculum
Consider Alternatives If:
- Your child struggles with self-direction or needs more structured guidance
- You prefer a faith-based approach to science and history
- You're looking for a comprehensive curriculum with less screen time
- You need a program with robust built-in assessment and testing tools
- You want a more scripted, parent-guided approach
Our Bottom Line
CK-12 Foundation offers impressive, free educational resources with outstanding STEM content. Its adaptive technology and interactive approach make learning engaging for many students. While navigation can be overwhelming initially and some subjects have less depth than others, the platform's flexibility, customization options, and zero cost make it an exceptional value for homeschoolers, schools, and self-directed learners worldwide.
Subjects covered
Core subjects: Mathematics, Science, English/Language Arts, Social Studies
Electives: Engineering, Health, Astronomy, Photography, SAT test prep
Special emphasis: Strong focus on STEM subjects, particularly math and science; interactive learning through simulations and multimedia
Grade level coverage: K-12, from Kindergarten through 12th grade
Teaching Format
Online delivery: Web-based platform accessible from any internet-connected device
Self-paced structure: Students progress through material at their own speed
Interactive lessons: Engaging content designed to promote active learning through text, videos, simulations, and practice exercises
Assessment approach: Built-in quizzes and adaptive practice that adjusts difficulty based on performance; instant feedback provided
Teacher support: Teachers can customize content, track student progress, and utilize auto-graded assignments
Implementation flexibility: Can be used as a full curriculum or supplement to existing programs; customizable FlexBooks for tailored learning
Download options: Materials available for offline use as PDFs or EPUBs
AI support: Flexi AI tutor available to assist students with questions and guidance
Pricing
CK-12 is completely free to use.
All textbooks, lessons, exercises, and features: No cost – no licenses to buy, no subscription fees, and no paid premium version.
No hidden costs: No “freemium” model; no limits or data-selling catches.
Open license: Materials are OER, allowing free use and printing.
Sustainability: Pricing model intended to be permanent and free for all users.
Parent Involvement
Moderate to High involvement required
Homeschooling: Parents typically act as teachers, choosing FlexBooks and modules, and guiding students through the material (initial setup can be time-intensive)
Daily commitment: Regular monitoring of student progress is needed, especially for younger learners who may require more guidance
Preparation: Parents need to plan lessons and select content, which can be overwhelming for some families
Assessment duties: Parents may need to check work, review scores, and request answer keys for open-ended exercises
Self-directed learning: Older or motivated students can work independently, requiring less daily oversight from parents
