So what your saying is your son messed up because he wasn’t mature enough to have a phone so you’re punishing your daughter for his behaviour?
My older 2 now year 8 & 6 we’re both given phones in year 6 in order to get use to having them for high school. It’s here we have ironed out any teething problems, mainly wats app group chats that turned messy. Neither of them join any group chats anymore and automatically take themselves out of them. The conditions around having phones are they belong to us not them. We check as often as we like and they ask permission before getting apps. Year 6 dd lost her phone privileges for 24 hours yesterday for a completely unrelated reason to her phone but she handed it over no arguments.
It was in year 6 we allowed them a bit more freedom, walking home from school going to the shops with friends. This is where a phone coming in handy. My oldest DD was hit by a car one day, she was ok but because she had a phone (her friend didn’t) the lady driving the car was able to call me.
Neither have been in trouble at school because of phones. Year 8 dd is not allowed to take her phone out on school premises without permission, the school have very struct rules, they will confiscate it if it’s seen. She never had any problems or been told off for this.
Both mainly use their phones for social reasons but also for school work. Highschool has apps that the kids need access to, she dose homework on her phone. With more freedom she’s able to stay in touch when she’s out without us.
I hate it when people demonise phones, yes some kids can’t handle them and need guidance but not all.
Dont punish your daughter because your son couldn’t manage having a phone at 11.