It's not worth any of it at all in my view
I was privately educated on a scholarship (not in a very posh selective place but still) and went to Oxbridge (rare occurrence from my school, no-one had been for years) to study a sought after subject and it was not enough of an amazing experience for me to want it for my kids. I enjoyed it but I would have enjoyed other courses too. I cannot fathom the level of over investment of some people in their kids education
If you are a parent who is interested in their DC education, reads to them, talks to them about the world then you are already giving them all the advantages you need to. You do not need to pay for private education, nor for tutoring nor move to a grammar school area. Obviously these places get stellar results they only take pupils who would always get stellar results and they weed out anyone who won't make it and even make you pay for it. What is the value added of any of these places? It must be tiny as there is no value they could actually add as the kids are all so clever anyway. It all seems like Emperors new clothes to me. Not to mention the effects on children's self esteem and mental health should they fail to live up to parental
expectations. I see the casualties in my work with their eating disorders, depression and anxiety
I have always sent my kids to the local school closest to where we happen to be living. The 2nd school had an RI Ofsted rating and all. Eldest didn't want to go to the hot house 6th form so I didn't make her. Still on course for 3 A*s and she'll go where she wants to study what she wants. She's happy and she loves learning and that is all that matters.
Enjoy your DC childhood. Chill out and save your money for books and experiences that back up what they are taught in school. Go to museums, art galleries, concerts, grow things in the garden, cook, visit historic places, talk about world events and what's in the news and you will automatically be giving your child so many advantages and enjoyment too.