IQ tests are not tests like a school maths tests. They are tests like a blood work-up. Perfect scores and number of questions correct aren't really the point. Your child is obviously very bright. The scores get him into school programmes. If you want more or better info you need a better test instrument. It may be worth it to apply for DYS but for now it may be better to see how the school handles it. If they do really well further testing may not be needed.