Have you used Khan Academy? Our teens have used it so much over the years (and still do), especially for Maths!
I used Khan Academy myself recently as I needed some further explanation on some Maths concepts for one of my university subjects. The lessons complimented the uni content perfectly and filled in the gaps I had so I could proceed with my assignment.
And something for my readers who aren't Aussies - they have a great section on Personal Finances with US information and links. So if you were a little let down by the Australian-centric info I shared here on Wednesday, check out Khan Academy! it's FREE!