Depends on how it’s enforced.

The data we have on bans on underage drinking and smoking show that they work. Some kids will still smoke and drink, but the number is reduced, drunk driving accidents go down, and eventually fewer adults abuse alcohol and smoke cigarettes.

The myth about age limits making it forbidden and attracting more kids to do it is just that it’s a myth. Spend some time looking at the studies. They almost universally show that age limits on drinking and smoking are harm reducing.

There are a few differences. For one, it's much easier to regulate the sale of alcohol and tobacco, the level of friction is much higher and usually involves an in-person interaction with an adult. Visiting some dodgy website or downloading a VPN is much easier.

Second, the peer pressure to drink/smoke has never been as strong as the network effect of social media. Almost all 15-year-olds are on some form of social media, I don't think you can reasonably expect they will suddenly stop wanting to socialise outside school. Their entire identities are built around their online presence; that was never the case with smoking or drinking, at least not on this scale.

I'm sure it will have some effect, but kids are clever, and they have lots of time, they will find ways to bypass these fairly weak bans. Imo, the only way to do this is to provide an alternative along with the ban, like what the Russians are doing with Max as a replacement for Telegram/WhatsApp, though that's not entirely successful either.

In a way, it's nice because young people will find way to circumvent the limits and they'll learn "hacking", just like we used to do in the very different internet we grew up with.

You can’t conjure up a bottle of vodka or a pack of cigarettes out of thin air in your bedroom with a cheap Wi-Fi only Android phone, but you can use that cheap Android phone to access social media.