Yep, they'll get it even if you don't buy it for them

No, they won’t. The schools have internet but they also often don’t even allow phones these days. And those networks block almost everything.

They might still get some content downstream of other kids. However, I doubt a “look at this tiktok” here and there has any harmful effects.

What’s harmful is excessive social media use, especially unmonitored. So, either monitor your kid or do not give them access. It’s perfectly fine to have a family computer in the living room if you’re worried about little Timmy looking up “boobies”. Problem solved, and I saved you some money.

I think a lot of parents do basically nothing and then are unhappy with the results. Yes, if you don’t try, you won’t get your desired result. But you can try stuff out, and you can always pivot if you feel it becomes inconvenient. The reality is we don’t need these complex technological solutions. There are simple, brain-dead solutions like “don’t give your kid a phone for hours on end” or “give your kid a flip phone”.