I usually just reply with age or "he would be in 2nd grade, but we homeschool". I get the feeling that's the answer people really want. He is working 2-7 grade levels ahead depending on the area, so there wouldn't necessarily be a good alternative response. He is small for age, so even saying he was a year or 2 ahead would get into a discussion about his size. I'd rather talk about his academic skills than his size! crazy