I was recently introduced to Mobymax. Mobymax is a sight for homeschool parents and teachers alike. My kids have fallen in love with Mobymax and it has a FREE package and a pro membership package. The pro membership is $99 for a full year for as many students as you'd like to add.
My kids and I just did the free account which was awesome. I was able to pick and choose what subjects I wanted them to have. This site did have a placement test that each child began on their level. My kids enjoyed seeing what level they were on. MobyMax is Common Core aligned and they pride them selves on being built "from the ground up on Common Core Standards." One of the things I loved about MobyMax is my kids could work on their level whether it was above or below their peers, or across different levels in different grade subjects. My oldest placed in 6th grade vocabulary, 4th grade math, and 4th grade reading, he is currently in 3rd grade. He loved that he was being challenged academically. My daughter loves that she can pick what subject she works on.