Our son was 12 when he got his first phone. Which was 7th grade. And even then his mom didn't want him to have one. So as I said I compromised with him and suffered my wife arguing with me over it.
That kind of surprises me. I should think all parents would be pleased for their kids to have phones simply as a safety issue. They can always get help if they need it.
Our son's biggest problem was taking his phone to bed and posting with his friends to 2 am in the morning.
Rather like reading in bed with a flashlight, but less constructive.