He should see a neuro psychologist in order to determine if there are any organic issues. In addition his cognitive and communication abilities need to be further investigated as you did not receive an answer when he was tested in school. If he cannot fill out a simple application it is important to find out what the impediments are and go from there. At this point all you know is that he has a significant problem. As to the the cause that is what you wish to find out. It would be purely speculative to try to determine the cause at this point. It could range from such things as attention disorder communications disorder to cognitive impairment. Some of the causes are amenable to treatment whereas others are irreversible and require adjustment in plans for future goals. Again I advise against speculation and urge testing and then go from there.
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