@scentedgeranium
My DC have very RP accents. partly as a result of having lived in a number of places and partly because me and DH are university educated. We all went to state schools (comps not grammars). But DC tho say that they lack the confidence of some of their less bright peers who were privately educated. My DC went to Durham and Cambridge and still feel less polished and confident! It makes me a little sad because everything else in their backgrounds suggests they should have utmost confidence. DD even said a few of her privately educated friends have been in awe at her exam performance, and yet they still have more confidence. The issue I suppose is whether this confidence gets the less able into positions of power and expertise which they do not deserve!
IME, confidence definitely does get the less able into positions of power & expertise (see current cabinet etc). Seen it so many times in different industries - academia all well and good, but confidence/veneer is what people see.
I always confused people as I boarded til I was 14, and then went to the local comp. Retrospectively, I'm grateful for having been to both, although was tough at the time. I've got the RP which undoubtedly has helped my confidence but I've also got the bantz and I'm not scared to walk into a situation with people that didn't go to private school (I was v scared of this whilst at private school).
I notice as I get older that I have a "broader" education in some areas than DH, eg I can recite poems and know about Renaissance painters 🤣. But in general I'm not sure it's worth the £. We never countenanced a private education for our DC, but then are lucky they have great state options.
As pp said above, I think the older you get, the less easy it is to tell.