You can only assess ‘worth’ based on why you are choosing independent education. For us it was never about the exams ( two probably did better than they would in State and one about the same) but I believe firmly that exams should be the by product and not the purpose of education. Education is the one gift that can never be taken away from you and in that it’s precious .
We chose a school with a broad curriculum of both examined and non examined subjects and lots of extra curriculas to develop the ‘soft skills’ . It’s not super selective but is selective to some extent , probably most are in the top half but there are plenty who might for example Find maths difficult but are a brilliant artist or tuba player for example .
I wanted outdoor space , long playtimes between lessons , school lunches , specialist teaching below 11 rather than the endless ‘topics’ , and crucially lots of opportunities to stretch them sideways and push them out of their comfort zone. Drama, music, sport for everyone and not just with those already confident enough to push themselves forward.And in the case of one child significant support with SPLD.
I freely acknowledge that we have been privileged to be able to afford this , but, and it’s a significant but, we have done it out of income , and it has come at a cost. The schools we chose were not the most exclusive either , approx one third receive help with the fees through bursaries ,
I don’t regret it at all but plenty would say that the local highly regarded secondary would have got them the same exam results .