If the tester is asking for something, I would bring it. Do you have any worksheets from school? Working on letters or anything? If not, ask your son to write something for you. I wouldn't tell him why or coach him to do his best. Just have him write an informal note, letter, story or a couple of sentences. You are trying to get an accurate evaluation done, so I would bring anything and everything that is asked for by the neuropsychologist.