Khan Academy is primarily a website chock full of useful content for learning, organized by grade level, making it an easy way to advance in line with the curriculum. The course materials cover math, science, art history, and more.
The idea behind the academy is also to help students learn based on their abilities. It isn't age-based, as grades in schools are, and so the extra optional learning platform allows those ahead or behind to advance further or catch up at their own pace.
Khan Academy helps students that struggle with a topic to become more proficient. It also allows those who enjoy a topic to learn even more, driven by their enjoyment. This should help pupils to specialize and find themselves doing more of what they enjoy. An ideal start in finding a future career.