Im a secondary safeguarding lead and have an observation on this.
I previously worked in a highly affluent and very highly achieving school. I now work in the opposite type of school.
In a high achieving school, with very engaged parents who keenly focus on the best possible outcomes for their children - many of these children don't have phones until 13yo / Year 9 and because this is fairly commonplace the children aren't that bothered by it. Similarly curfews of 9pm on school nights though to the end of Year 13 are not unusual, except for one-off occasions. In winter we will routinely see parents only allowing organised events after school because it gets dark early. Socialising is usually done at sports clubs and extra curricular activities - so with adult supervision only.
It's interesting to see that much of what I thought unreasonable or unrealistic as a parent of a teens myself, happens routinely in circles with high investment of children's outcomes.
Compare to the sink school, in the rough area of a socially deprived inner city where I now safeguard.
It would be unheard of for a child not to have a phone in Y7, and usually have all the 13+ social media apps too upon arrival in Y7. I would say parents let kids go out much later, and stay up much later.
This leads me to many a sociology pondering. If the sink school parents took the same approach as affluent school parents, to what extent would this change outcomes? How much of these two parenting styles is down to peer pressure from other parents? How could society change this? Anyway, I digress....