My DD10 has taken the CogAT twice (several years apart, as it is normally scheduled) and we never found out the age vs. grade on her second test, but we did see both for her first. DD is on the young end of her grade. For Q & N, her age percentiles were very slightly higher than the grade percentiles. For the V and the composite, however, the percentiles were identical.
I understand why it doesn't seem fair, but I think whether it is a good plan on your school's part really depends on the program and what it is attempting to do. Let's face it - our "younger" kiddos received some "extra challenge" the first day they walked into school and were learning the very same thing as the "older" kids. If the goal is to identify gifted kids and challenge them, then your school's plan is poor - they will miss some "younger" gifted students. But if the plan is very utilitarian - to challenge those who the regular school program is not already challenging...more of those needing challenge might just be the students who are already older for their grade.
