I can tell you that holding a kid back a year is a common occurrence in Southern California. A coach suggested we consider holding our son back in the 7th or 8th grade. He is an end of May birthday. We chose not to. He is at a public school, and appears to be doing well academically and socially.
However, be aware that at some Catholic and private schools, if you are not a hold back, you will likely be one of the youngest and smallest at freshman tryouts. We know of good players at a particular school who did not make the team, basically because they were a year younger than most of the other boys.
i think it’s worked for our son during summer travel ball, much better competition against the older players. It’s ultimately up to each family, just telling you how things are in this area.