I am not sure how you would effectively gauge "written exprssion two years above" but there is a huge difference between an average 3rd grader's writing versus a top 3rd grader's writing. I would venture to guess that a top 3rd grader's writing is probably superior to an average 5th grader's writing. When DS/DD started 3rd grade, the teacher on Back to School night showed the parents samples of work from the previous year's top students and they were pretty impressive - well-developed paragraphs with strong vocabulary and correct grammar/spelling. I think the teachers at your DS' school would be a good source for the standards that would be appropriate for your local HG program. After all, the writing standards also appear to vary from school district to school district.
