honestly, is it a status thing? My in'laws only have two grand kids - our two! They offered private school from 4-18 years and we said no, it's now in trust for the kids!
We said no because in our situation, we did not feel it represented a good use of a resource (capital ££), our local schools are fine and we support our children at home. The local independent school didn't get massively better results and isn't a "top tier" school - very ordinary local people send their kids there.
The private school further away (in my opinion more prestigious, well known and "famous" alumni) was a 24 mile trip one-way and school bus left at 7.30 am. Transport costs added up for two kids!!
What is better about the private school and why do you think a state school is not a good fit?
Doesn't sound like it's very affordable and will both children be given the same opportunity? Can you affords ski trips, the extra expenses: sports clubs, trips to Europe, music lessons and can you also save for their future uni, deposit on first home etc
What is your DDs personality - is she resilient, sensitive, does she tend to get on well/mix well? is she good academically without too much pushing? Is she strong, determined etc?
Our eldest is going to a state secondary and it is regarded as fine locally, there is another less popular and another one very popular (get a few % better GSCE results,. all three high schools are OFSTED good. All three have a massive focus on building up life skills, team working, doing presentations in lessons in front of peers etc.
Is it really worth it the money and what are you really expecting from school? Honestly, is it connections and better environment?