Are you worried about your sons ending up as massive arrogant knobs? I've had three family members who went to top boarding schools, including Eton and King's Canterbury, and let's just say, they really do think they're the dog's bollocks. And I've worked with others, too. I've found them petty, ultra-competitive, EXTREMELY shallow, and, yes, arrogant. I've also had a flatmate and a husband who went to those sorts of schools, and they both lived similarly. You could tell that they had been brought up in institutions. They lived in pigsties, basically. The flatmate went to school with Camilla's daughter in the Nineties. Said she was very quiet.
But there's no doubt that the education is wonderful and the people who went there do have a wonderful sheen of confidence. And you get dreadful types at state schools, too. Sadly though, in my experience the public school label as being absolutely full of themselves and boastful, including as adults, is well-earned.
I went to a top state school and got better grades than most people I know who went to these top schools, which is how I have studied, worked, and lived among them!