It may be that you have both an age percentile and a grade percentile on your report, rather than two age percentiles. Some schools choose to have the SAI calculated for both. (The SAI and the percentile are derived from the same underlying z score, but in this case, both SAIs would round to 99th %ile.) There is generally a small difference in favor of the age percentile if your student is young for grade, and in favor of the grade percentile if your student is old for grade (e.g., just missed the birthdate cutoff).
