Slug: I have also worked in both, and I'm intrigued by your comments.
Dodgy financial practices
Examples?
Unqualified teachers (very common in private schools) You know things are bad when the kitchen staff are routinely more qualified and educated than the teaching staff.
Expand, please. Kitchen staff are undeniably better qualified in kitcheny things - but if you're trying to say that the kitchen staff have PhDs and the academic staff have NVQs in food technology, I don't believe it. But, yes, there are some teachers in private schools who don't have a PGCE - though they'd struggle to find a job in a private school now.
Managing students who are unlikely to achieve academically out of the school as soon as this become obvious.
Yes, I came across that. State schools have other ways round this (like getting children statemented).
Coursework submitted to the exam boards that bear little (if any) resemblance to the work submitted by the student
Yes, in both types of school.
Exam practices that raised eyebrows
Like what?
Snobbery of truly epic proportions (and not just the students)
Yes, in both types of school.
Racial and sexual harassment routinely left unchallenged for fear of alienating the paying customers
Yes, in both types of school - though without the paying customer excuse in state ones.
As much violence and disruptive behaviour in private schools as in state ones.
Yes, there can be disruptive behaviour. Private school does not guarantee a cohort of well mannered, considerate children, esp. at secondary level (when you get an influx of children from outside). IME, though, private schools are quick to expel for this, and can do so quite easily.
I fear, Slug, that your post is yet another variation on the 'private school children all take drugs' theme. No school (either state or private) is perfect, and no school that consists largely of teenagers is going to be free from problems of one sort or another. But on balance, I would still say it is more than worth it for the range of opportunity (which, admittedly, some children don't give a toss about, and take completely for granted) and for the quiet confidence that good private schools manage to give even the dimmest pupil.