CK-12 FlexBook 2.0

CK-12 FlexBook 2.0 is a free platform for customizable K–12 digital textbooks, lessons, and practice. It suits educators who want to adapt course material and track class progress, and students who benefit from interactive lessons. Its breadth of teaching tools is appealing, though not every core book has been converted and some interactives need a larger screen.

Overview

FlexBooks cover K–12 subjects including science, math, and social studies. Lessons can combine reading with PLIX interactives, simulations, adaptive practice, and related learning materials. That range lets educators pair instruction with activities and practice, while the content available varies by subject and book.

Educators can reorder chapters and add or edit material in a customized FlexBook. This makes FlexBook 2.0 a useful fit for teachers shaping a text around their course. CK-12 is still converting its core content, so educators should confirm that the books they need are in FlexBook 2.0 before making it the foundation of a course.

Key features

Practice and classroom assignments

Adaptive Practice draws from a library of more than 150,000 questions and adjusts its selections in response to student answers. It gives learners practice that can respond to their performance, rather than a fixed sequence. Teachers can assign lessons, interactives, videos, and practice to an entire class or differentiated groups, then review student progress reports.

Access and accessibility

The platform works in a browser on laptops, desktops, Chromebooks, tablets, and mobile devices. Standalone Simulations and PLIX Interactives require a tablet-size screen or larger, which can limit their usefulness for students relying on smaller phones. Readers can adjust font size, background color, and line spacing; lesson text also supports text-to-speech and Google Translate.

Users can download PDFs of FlexBooks they create or customize. Interactive content may not render in a PDF, and CK-12-created PDFs are not downloadable, so offline access is more useful for adapted books than for the full interactive experience.

Integrations and support

CK-12 lists Google Classroom, Canvas, Schoology, Kiddom, Clever, and ClassLink as SSO or LMS partners. Users can contact CK-12 Support by starting a ticket or sending an email.

Pricing

FlexBook 2.0 — free. The free plan provides an online customizable digital textbook, with content varying by subject and book. It includes the core combination of editable books, lessons, interactive activities, adaptive practice, and teacher assignment tools, with no paid plan needed for the stated offering.

The main trade-off is availability: some core books have yet to be converted to FlexBook 2.0. PDF downloads also do not preserve all interactive content, and CK-12-created PDFs cannot be downloaded. This plan is a strong option for educators whose required books are already available and whose learners can access suitable screens.

Platforms

FlexBook 2.0 is available on Android, iOS, and the web. CK-12 says its browser experience works on laptops, desktops, Chromebooks, tablets, and mobile devices. Standalone simulations and PLIX activities need a tablet-size screen or larger.

Who it's for

FlexBook 2.0 is designed for K–12 educators and students. It is especially suitable for teachers who want to customize a textbook, assign different materials to groups, and follow student progress. Students can use its readings and activities for science, math, social studies, and other covered subjects. It is a weaker fit when a required text has not been converted or when learners mainly use small-screen phones for standalone interactive work.

CK-12 says it uses administrative, technological, and physical safeguards and encrypts information transmissions using SSL or similar technologies. It also says it does not sell student information or use or disclose it for behavioral advertising to students.

Pros and cons

• Pros: Free access combines customizable textbooks with lessons, interactives, simulations, and adaptive practice, giving teachers several ways to support a topic.
• Pros: Teachers can assign materials to classes or differentiated groups and review student progress reports.
• Pros: Font, background, and line-spacing settings let readers adjust lesson presentation, with text-to-speech and translation support also available for lesson text.
• Cons: Core content conversion is still in progress, so some books may not be available in FlexBook 2.0.
• Cons: Standalone PLIX Interactives and Simulations need a tablet-size screen or larger, limiting access on smaller phones.
• Cons: PDFs may lose interactive content, and CK-12-created PDFs are not downloadable.

Alternatives

Consider K–12 Curriculum Platforms or Open Educational Resource Platforms to compare broader sets of curriculum and open resources. For a focus on books, see Digital Textbook Platforms; for science-focused options, browse Science Learning Software.

MobyMax is another option, with a limited-access free educator version and a paid Family plan. Khan Academy offers a free plan and paid school and district licensing. Choose Amplify Classroom if free interactive K–12 math, literacy, and science lessons, a Teacher Dashboard, and Polypad virtual manipulatives suit your needs; its individual educator plan offers only partial content customization.

EL Education Curriculum is a free alternative for educators seeking language arts resources, with an account required for some. Eureka Math offers free PreK–12 PDF curriculum in student and teacher editions, while its Digital Suite is custom pricing. Illustrative Mathematics provides a full TK–12 curriculum online at no cost, with downloadable and printable teacher and student PDFs and no time limit. Oak National Academy offers free access without paywalls or package tiers. OpenSciEd offers curriculum downloads at no cost for educators or parents, with registration required.

Verdict

Choose CK-12 FlexBook 2.0 if you teach K–12 and want a free, adaptable textbook platform that pairs lessons with interactive activities, responsive practice, and progress reporting. Its strongest case is the combination of customization and classroom assignment tools at no cost. Look elsewhere if a core book you need has not yet been converted, or if your learners need standalone interactives to work on phone-size screens.