When we got CoGat scores they gave us age-based and grade-based percentiles. The age-based gets around the red-shirting issue since they are normed for kids the same age regardless of grade placement. They did not give us scores in the "150" format. When I asked, our GT department said that the "150" format misleads people to correlate with IQ so they only gave percentiles. The version that my daughter took in first grade only had about 40 questions per section. A perfect score correlated to 99th percentile. I seem to remember that missing one dropped it to 97th.
