Where to start?

My friend didn’t finish sixth grade, and he’s 38 now. He’d really like to get his GED but while intelligent and literate, he needs more support than the general GED classes offer. I’ve done a lot of googling but I’m not sure I’m using the right terminology - he needs some building blocks - lessons that will get him to the hs level so he can understand the GED prep material. Suggestions? Anyone else in this boat?