I'm no expert so I can't really offer an advice, except to echo what others have said (Try Sylvan only as a last resort--they are way overpriced and an individual tutor could probably do just as well!). My mom once told me that my kindergarten teacher was going to recommend that I be retained--yes, I was about to fail kindergarten
--but apparently I improved so much during the last couple months of school that I got to go on to first grade with the rest of my class. Maybe it'll be the same in your son's case...there's still time!