Confidence comes from knowing your place in the world is secure. That can come from having a high level of self belief or from knowing there is a very good support network around you and that support network has the expertise to help you be a success at the next stage and beyond and that if things go wrong, you will be rescued and a new route planned for you.
Some parents can provide all of that. Some can provide some of it. Some can provide very little of it. Where parents can't provide all of it, independent schools are very good in filling the gaps and so ensuring a child's place in the world is more secure and there is access to more opportunity and expertise to allow them to become successful at the next stage.
Lots of middle class parents in all school systems can give their children lots of love and access to extra curricular activities and opportunities. Some will also be able to provide opportunities for extra help with school work difficulties, or espertise about GCSE and Uni choices, or access to individuals who can provide work experience, or a circle of friends who have similar aspirations. Most apprentice cannot provide absolutely everything to ensure all opportunities are catered for....most decide that doesn't matter anyway.....but perhaps what some good independents do,is to provide some of the things that even dedicated parents might struggle to supply, or to supply on the scale and level which a decent sized indecent school with a history of preparing children for successful futures over possibly centuries, have done.
And a key part of it, for parents and children too, is knowing that they are getting something that most people aren't getting. That can build confidence, becaue often confidence is a comparative thing....that's perhaps the less attractive side of it, which people often call 'entitled' - and whilst much confidence needs to be inner confidence, to be really sustainable, the perhaps more superficial confidence which comes from knowing you have the back-up behind you which most people don't have, isn't as sustaining in the long term, it's often good enough to get people to the next stage, and as success occurs, conside de starts to naturally grow anyway.
So, if you passed an exam for your Prep at 8, you already feel a success. And if you play for the school team and pass Grade 1 on the piano and know some children don't do these things, or failed the exam you passed, or didn't even have an opportunity to take it, you can feel pretty good. And then when you hear in assembly every week about the successes and achievements of your peers and how the older ones went onto prestigious schools, you believe it's there for you too....it starts to seem normal and likely, rather than remote and unlikely. And when you then spend time with other children from successful families and see their lives and confidence and expectations.....it all starts to feel very normal for 'people like us' even if you are only 8 or 9 and can't even articulate it. And if a one off failure occurs, there are plenty of people to pick you up and tutor you, or find a new activity to be successful in, or a new route and so failure seems like a short term blip rather than a lasting thing to be afraid of. And then you go onto your next school, which again, you probably had to take an exam for and even if pretty much everyone gets in, as is the case in lots of independent schools, there's still a sense of success and knowing you are having something others don't........and schools have to justify their fees and remind parents and children of the extras they are getting, so even if they aren't actually that significant, belief in their existence and the fact others aren't getting these extras, perhaps breeds confidence, even if it's not particularly warranted...but that doesn't matter, becaue much of confidence is the belief itself rather than if there is substance to it underneath. And as you grow, you see there are always those 'like you' around to help you and protect you and carry you forward....so why would you lose confidence, because 'people like us' can usually work things out, so there no need to fear and in the end 'people like us' ar in charge and look out for our own.