Im my state (Texas) they don't do it anyway because school is not required until 6 as a 1st Grader.
Mine was mentally and emotionally ready for kinder. Holding her back would have been harmful. Only you know your child. How does she act with kids younger?- If she is bossy, holding her back won't help that at all.
My brother however was a big baby so my mom held him back even though he turned 5 the same month school began- it was good for him!
I homeschooled for K and put her on the list to test into a Charter school.
I then decided to homeschool for good