Hi,
It's difficult to organize thoughts onto blank paper. This might help: Try sitting down with him and have him think of a topic exciting to him, one where he'd have to make his points. Help him make a main assertion. Write that down. Next, he thinks of an idea/statement to support that. Put that on an index card. Do another card, etc. Ask for examples/illustrations for those points. Write each on a card. When all thoughts are on cards, have him organize them on the table, play with arrangement, etc. This may be easier before he hits the paper. When I was younger, it worked for me.
