I have a nephew exactly that age and I've seen up close how the family handles this. The thing is, 11 years old is that point where some kids are already ready and others still aren't, and it depends a lot on the specific child. My brother bought him a phone at 10 because he needed to communicate when he left school on his own, but he set clear rules from the start: no social media until 13, limited screen time, and the idea that the device was mainly for emergencies rather than anything else. At first it seemed like a punishment to the kid, but he adapted well afterward.
What I see with other cases is that a lot of times social pressure is real but it's not as dramatic as it seems either. Yeah, there probably are kids with phones in class, but I'm pretty sure there are more than you think who don't have one or share theirs with their parents. As for academics, at that age the risk of him getting distracted is pretty high. I've seen kids who start secondary school fine, but once they get their own phone their performance drops noticeably. If you can wait until 12 or 13, it's probably better.
My suggestion would be that if you decide to buy it sooner than you planned, do it with structure. It's not the same thing having a basic phone or a low-end one for emergencies as having a full-featured smartphone with access to everything. And if you wait a couple more years, honestly, nothing bad happens. His friends are going to stay his friends, and at that age the dynamics change constantly anyway.