Meet HIS learning style. I agree with Martha, keep him active doing something he enjoys - jumping on a trampoline, running, tumbling, hiking... get some of the physical energy expended and he will have more ability to focus after that. Do things in smaller bursts. Many kids kind of "stall out" at this age, and then they mature a bit more and are able to refocus and gather a lot of information in a shorter amount of time.

If a child has an environment that has interesting things to look at, listen to, read, touch... they will learn. Kids (well, adults too) learn what they need, when they need it. For example, if a person's brain is ready to learn say, algebra, but they are not interested in algebra, it will be a struggle, and retention will usually be low. If that same person finds a passion/career path that needs algebra, they will then be motivated to learn algebra, and retention will be higher. If a person's brain is not yet fully wired in the area that algebra is learned, then they will not comprehend it. When it fully wires, no matter what age, if they desire to learn it then, they will. Pushing and expecting it will not make it happen.

My boys both inproved in writing, grammar, reading... when they were involved with online gaming with other people around the world. They wanted to present well, so they started asking "how do you spell. ___?", "does this sentence make sense?", "how do you pronounce___?" All of the sudden these things had a purpose in their lives and within a few weeks they were "caught up" and moving quickly ahead. It became relevent. If your son wants to take over the family business, then having him actively involved in learning the componants of the business instead of following a curriculum or a scope and sequence then I bet you will see him blossom, especially over the next few years when he is further along in puberty and maturity.

Stepping back and re-evaluating what fits him best, what is of most interest to him, what hasn't worked... all give you a fresh perspective and allows you to let go of what isn't in his best interest. Just because it is "tried and true", "what has been done for years", "the experts say so"... doesn't mean it is best for your family, your individual children. You are the one who knows your children best, and by listening to your child, their wants, their needs, their desires.. you will be better able to partner with your child and help them learn more naturally, more personally, more effectively for now and the rest of their lives. Don't worry about "catching up" as your child is not "behind" they are just where they are. Just keep moving forward, joyfully, from there.