If I were you, I would ask your kid about the part of the test where he had to read a bunch of allegedly-nonexistent words ("nad" used to throw me in the old list, as it is slang for gonad).

You'll want to have some clue about what was going through his mind while you're sitting in that meeting. Nobody qualifies for Special Education because they can't spell. And few children have any trouble with spelling in a language that is regularly spelled (Spanish, for instance).