DS12 is taking a Self paced math class with JHU/CTY. So far it's been good. He moves at his own speed and the instructor has been very quick to respond to any questions he has for her. They have meet on white board if he need mores explanations. He is taking a HS level, so I can't speak for the lower level classes. He seems to be doing well with it. He is very independent on the computer and emailing his instructor. We only see the copies of emails because he really takes care of everything himself. He also uses ALEKs for any addition practice time he needs or wants. He will complete the course in 3 months. We have not used EPGY. I do believe JHU is cost more. I'm don't know if they have self paced classes for lower levels or not.
The 8th grade level could vary a lot by district. I would imagine at least through pre-algebra levels in our district. You might want to fine out what the standard placement for 8th grade is in your district. I got DS on board with summer math a few years ago by suggesting (in a very vague non discript way) that his placement might be better in the future if he worked on it over the summer. He got 3 skips in row for his efforts and he is always on board now:)
The last couple of summers he has just used ALEKs to prepare for a skip. He needs the transcript for credit this year otherwise we may have just used ALEKS. JHU uses Thinkwell videos for the class. If you just want practice and new concepts maybe Thinkwell & ALEKS would be cheaper.
