At that AGE I don't think they need one
At that STAGE I do think they need one
I think I'd be happier at 13 - teenager, various apps become age appropriate at 13 etc, but I accept that they need one once they reach high school for various reasons. A lot of kids did have them in the last couple of years of primary but I held off until the summer before high school.
My eldest two have smart phones, they aren't the latest phones as I don't want the worry of them being stolen, but they aren't ancient either.
They are allowed WhatsApp, despite the age limit being set higher, but things like tiktok etc they use the app on my phone to learn tiktok dances so they aren't the only one who doesn't know it, but don't have it on their phones/their own account
We started, and kept, with rules about phones being downstairs before they go to bed, no phones when we have visitors - their friends obviously excluded if they are all on their phone, but not when my parents or sisters etc come over, no phones if we are doing a family activity - except for a quick photo....
I stick to these rules too though, so it's leading by example and seen as being fair.
They know that I can look at their phone at any time, I always ask first and they are happy to hand it over. I don't do it very often as I trust them and they've proven that they can be trusted with the phones. They know that they can ask my advice about messages they've received / how to reply etc, so if there was any cyber bullying going on I do think I'd be aware of it (I'd also check their phone if I noticed change in mood/behaviour, so likely to pick up on it)