Some free online education resources are KhanAcademy.com, CK12.org and NeoK12.com. These websites offer free educational materials in different subjects for students in grades ranging from kindergarten to 12th grade.
The Khan Academy website provides more than 2,700 free educational videos in K-12 math and other subjects, such as chemistry, biology, physics, economics and the arts and humanities as of 2015. Additionally, this site has math videos for advanced math topics that include differential and integral calculus. There are also practice problems that students can try. If students get stuck on a problem, they can ask for help by clicking on the Hint tab.
The CK-12 Foundation provides access to educational materials in subjects that include math, science, astronomy, history and English as of 2015. This material is intended for students in kindergarten through 12th grade. CK-12, which is a nonprofit organization whose mission is to reduce the cost of textbooks and education, makes this material available by publishing web-based textbooks called FlexBooks. The CK-12 website also provides free SAT prep and many resources for teachers at CK12.org.
At NeoK12.com, there also are educational lessons and videos for different math and science areas, the human body, geography, social studies and earth and space. The material is for children in grade levels from kindergarten through high school. The site also provides puzzles, games, interactive diagrams and quizzes.