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The Nova Labs section in the Partner Content section of Khan Academy has material that is very easily understandable. While the same material would often put the content to a post high school crowd, the short videos (2 to 6 minutes) with clear content and great graphics makes this partner content great for middle school and up. Even an above average elementary schooler would probably find this section interesting and enjoyable. This is a section that is truly for all ages. They cover variety like evolution, cybersecurity, RNA, Sun/solar system, energy and clouds.
There are also quizzes, which are very easy to get all right if students watched the videos. Speed and accuracy badges are easy to get here, it'd be a waste to not get them. If you've ever heard of the "Sun 101" hack, a quiz in this section used to be hacked. Late fall/early winter 2015, Khan Academy rearranged the content to combine these 1 question quizzes into one larger quiz, thus making the item going around useless, but maintaining the content.
- RNA: the wonder molecule
- The Sun and solar storms