FWIW, Khan Academy is pretty well aligned with Common Core, at least in terms of material covered: https://www.khanacademy.org/commoncore/map

I think a lot of what people complain about with Common Core is bizarrely written school materials that were developed by some bureaucracy and don't make a whit of sense to an adult who already knows the skill, let alone to a kid. Khan Academy definitely does better on that count in my opinion, so it's a good supplement.