Khan Academy is great, but for anything you’re going to need to sit down there with them. I’d start with the grade level test to see what they are missing then

Khan Academy is great, but for anything you’re going to need to sit down there with them. I’d start with the grade level test to see what they are missing then you can hone in on that. Or if they are missing some core concepts you can go back as many grades as you need. With an hour per day of _your_ time as well as theirs they can plow through multiple years of material in months.