I oppose redshirting generally and have read a number of studies that support my feeling. However, there is also some troubling evidence that kids who are young for grade get misdiagnosed with ADHD at alarming rates. I could dig up the study but it's likely findable. Anyway, that might be a worry for me if I had a boy on the borderline AND thought he might be at risk for being incorrectly flagged for ADHD.