My neighbor was also terribly worried about his son's future. Go to the school. Especially, find out how Joshua has been taught. They'll talk to you. Many parents seem reluctant to ask the school for information, but they shouldn't be.
Schools keep a permanent record on each child.
That record will include various test scores and probably anecdotal information from each teacher. If you insist on your right to see the records in your child's school file, you may discover the answers to your questions about his or her school progress. You may also prompt the school to look more closely for a solution to your child's underachievement problems. No low-performing child need ever arrive in the fourth year of school without having received a specific analysis of the problem and specific attempts to help that child achieve success. The consequences to your child of repeated frustration may have devastating long-term effects.