Oh okay, your wife has worked in both settings. Yes, there are good and bad private and state schools. Am I right in assuming that she has come to the conclusion after working in both settings that private education would be best for your child(ren) in the future?
That's the short version, yes.
Her time working in state schools did not, in her words, produce any reasons why she would alter her initial belief that she would prefer private schooling for her children. I suppose there is an initial bias to consider, but her working in the state sector goes some way to balancing that out.
From my perspective, I enjoyed school and didn't have any complaints. I got a decent set of GCSE results, 12 different subjects between A and C grade (back when A stars didn't exist). However, when I got to postgrad level I felt it was very, very noticeable that it was the state-educated students, myself included, who seemed more likely to struggle with higher academic study. We were very much in the minority on the course too, and my experience was that my privately-educated peers seemed to have experienced a greater depth and breadth in their schooling - several of them spoke multiple languages, could play musical instruments, excelled at a variety of sports and had wider interests that were quite varied. My state schooling hadn't PREVENTED me indulging in any of these things, but their private schooling had actively encouraged their participation.