Yr 7 is a whole other game we found.
I treated the last term of yr 6 as a training and learning ground for yr 7. So the kids all had phones at the Easter, and had WhatsApp. It was all monitored.
As a pp said, the minute these kids get their phones some go crazy, and some aren’t monitored. This makes for some great learning moments on how to interact, when to walk away, and when to notify a parent etc. But on the whole, the kids are young and while some interactions are questionable, they are not adult in content. It settled down by the end of the year.
Some of the yr 7 group chats were horrific. The language and content on the large whole year groups was not ok. I felt that without the introduction at a ‘lower’ level, yr 7 would have been a whole lot harder to negotiate for them. As it was, they were comfortable in coming out those groups, knowing when to walk away and not engage and not worrying about the repercussions of doing so in the classrooms the next day. They were also comfortable talking to us about anything that came up that worried them, as that is what had happened in yr 6.
Should add their primary was very small and sheltered. Socially, moving to secondary was a big deal.