I would also send an email to the ex explaining your son's difficulties in school and ask him if he would help your son during his visitations. And keep him updated on his son's grades in school. If he doesn't do anything, at least you've kept him informed and asked that he help with your son's education just in case anything should come up.
Also keep in mind that you have to keep your child's best interest at heart, even if it means you have to spend more time with your son on his studies than your husband does. To me, it should always be in the best interest of the child, regardless what problem you may have with the ex.
Also keep in mind that you have to keep your child's best interest at heart, even if it means you have to spend more time with your son on his studies than your husband does. To me, it should always be in the best interest of the child, regardless what problem you may have with the ex.