I would suggest a couple of refinements of the accommodations suggested by the school psych and you:
1. typed response (this should include all the usual word processing supports, such as spell/grammar check, thesaurus).
2. supplementary oral assessment (teachers pull him aside after a test and say, "this is what you answered in writing for this question. Do you have anything to add?")
3. starred items only to demonstrate mastery of learning standards (this is a version of the reduced work load suggestion: teachers asterisk the key items on an assignment that will allow them to assess his mastery of state or local curriculum frameworks. He completes all of those items. If he completes any additional items in the assignment, they have instructional value, but if he doesn't, they don't count against him.)
And yes, four hours a day of homework is too much for an eleven year old. (Personally, I think two hours is too much, but I know a lot of high-achieving schools expect this.)
