What would happen if you had a 'family math review' every August,just to brush up? Any bribes he's been hankering for? Have you tried this already?
I make it really clear to my son that certain kinds of learning is 'understand once and have it for ever' and certain kinds are 'every year we make a groove in our brain, and then when we don't use the info for a while, and our brain has grown, the groove is more faint, so we need to re-learn again. Luckily since the groove is already there, it will be faster each time.
Best Wishes,
Grinity
