I teach math in the classroom, and have incorporated Khan Academy for going on three years now. Last two years was high-school level (though admittedly, with a student population that struggled at 1-3 grade levels behind where they needed to be), and this past year I've been working with 6th, 7th and 8th graders. Khan Academy is a great tool for allowing students to self-direct their work on math topics. What I like to do is assign struggling students to one grade level lower and stellar students on grade level, and then let them choose what kinds of topics they will practice. Best way to get students to buy-in and utilize it appropriately, I've found, includes 3 elements: #1) Grade students using an algorithm that includes active minutes as well as newly mastered topics; #2) train students to always copy down the skill name, an example problem, and their scratchwork (can do this by making it a weekly 'binder check'); and #3) train students to understand how to use the 'Show Hint' feature, in order to not get discouraged / empower themselves if you are not available to coach them through a rough spot.