This website is rubbish.
I say ages 10 and up, because Khan's style doesn't work for an age group any younger than that, but in all honesty, I don't recommend this website at all. Honestly, I don't understand why it's so popular. I suppose I like the style of the newer videos-- it's still on a pad but it's neat, organized, and appealing. But some of the older videos are still used, and these are a lot uglier with poor resolution, and you can just tell that they're aged compared to the new videos they're mixed in with. Here's an example of what I'm talking about: https://www.youtube.com/watch?v=wlB0x9W-qBU (newer video) and https://www.youtube.com/watch?v=2WS1sG9fhOk (older video). As a student in physics, I was looking forward to using Khan for physics, until I saw that it was incomplete (nothing on modern physics) and used a lot of old videos. Khan should really replace these old videos and work towards completing subjects. Khan Academy is advertised as this universal learning tool, but it's really not. It's not just physics, either. I looked around the website, and figured out he does this with a lot of subjects, like pre-calculus (which I'm taking next year). It's just annoying. There are also quizzes, and the videos corresponding to the quizzes are sometimes irrelevant to the skills practiced in the quizzes. It's very frustrating. I am impressed by the coding lessons, but Codecademy and other sites teach it better, and with so many other turn-offs on this website, it's hard to approach that. It's too bad that Khan Academy isn't everything it could be. I definitely would not recommend this as a learning tool. It' s garbage and an utter disappointment.