It's a bit tricky, as the "privileged upbringing" also often involves heightened expectations of confidence (part of entitlement) and most of the life, especial

It's a bit tricky, as the "privileged upbringing" also often involves heightened expectations of confidence (part of entitlement) and most of the life, especially early, is within a peer group who have similar privilege or lack of it. What would be an achievement for a less privileged family would be expected as table stakes for a more privileged one - you won't be compared (and won't compare yourself) with people who succeeded despite all the hurdles, the comparison is against what other people with similar (or more) privilege did by exploiting every advantage they had. So this creates a systematic exaggeration of your confidence and competence combined with the fact that you're always seeing everyone else's exaggerated competence and entitlement so that your actual competence does not compare favorably. Such a situation can easily lead towards imposter syndrome and low actual confidence combined with a faked posture of high confidence - even if actual competence is expected to be good compared to poorer classes as socioeconomic status does (on average) lead to better skills due to better opportunities and other aspects.