I am confused by red shirting.
US state laws have a minimum compulsory age to begin school of age six (24 states), age seven (14 states) and age eight (2 states). http://www.ncsl.org/documents/educ/ECSCompulsoryAge.pdf
Only eight states are age five.
It seems cutoff dates are seen as the required age but in reality they are not, they are to send children a year earlier than the law states to begin education.
Shouldn't this this be the exception and not the norm?
I live in one of the 8yo states, and "begin education" is a bit of a misnomer. It's a truancy law, pure and simple, since it's based off compulsory attendance. A child must be accounted for by age 8, either enrolled in school or registered as homeschooled.
And in our state it is the child's birthday that counts, not the start of the school year that they turn 8, so really a child could wait until their birthday to start school, though I doubt that ever happens. Because our compulsory age is so old here, the only people really aware of it are the ones intending to homeschool. My 9yo is registered, my 7yo not. Parents who fully intend to send children to school are rarely aware of the age of compulsory attendance here, IME.
So, yes, they are the required age, not a year before, at least in WA.
Otherwise, I'm a little confused by what you think should be the norm.