"It's not that impressive that your kid a year or two older than the norm for the grade can out score kids of the appropriate age for the grade... I'm guessing if the district would age base admission testing the red shirting would diminish greatly."

Jtooit, that is an interesting thought. The ACT and SAT could also norm the results by age, irrespective of what individual school districts choose to do. This may be a more equitable representation in terms of National Merit Scholarship, college admissions, etc?