There is a terrific website to help your children learn math, The Khan Academy. They have excellent videos. I wish this resource was available when I was in high school and college. I mention this site, not because it is an excellent resource, but because they have failed, failed miserably in a basic way.
When one goes to a page to watch a video there is breadcrumb across the top.
There is even a nice feature where a drop-down appears and one can select other videos in the same sub-category.
However, should you decide to see a video in another category - you cannot select a higher-level category. You are forced to go back, in a convoluted way, to the "index" page. Part of the problem is that some categories have a LOT of videos. Still, there are nunumerous workarounds to that problem.
There is one other issue. The Khan Academy is trying to increase participation by using gamification techniques. It's an excellent idea, as you watch videos you get "points." It provides an incentive to join the community. That's excellent. However, should you decide to join, you must login with either a Facebook or Google account. Tsk. tsk. Not everyone wants everything they do to be so easily and completely tracked by Facebook and/or Google.
All that being said, I still highly recommend this site.