I love Khan Academy! I use it all the time to do math! I don't know anything about the coaching system as I use it alone. To access higher levels (I know it goes up to calculus, I'm cannot recollect what else it has at the moment) at the top left side of the page there is a box that says "Learn" move your mouse to hover over that box (you may have to click it), then move your mouse down to to where it says "Math" hover over that, to the right a box pops up showing all the different subjects in math they have, from there you can choose which you wish to study Unfortunately they are mostly just videos and not interactive activities (though I think there may be a few, depending on the subject). I realize you posted this subject a while ago and may have already resolved your issue, but if you haven't, I hope this helps!