I'm really excited about this site to use for self pacing! It can walk students through the basic setup, as well as problems for them to practice. After going through this site, I would recommend the Symbaloo link as well.
On this website, you will find most every concept within the Common Core with practice related problems. Students can get immediate feedback as to if their answer computed was correct. THERE IS A COST INVOLVED, SO ASK PARENTS FIRST!