I found horsemadmom's original post, quoted here, deeply patronising and offensive, personally:
" The standards (work, behaviour etc.) will not be a shock to prep kids. However, One of DD's BFs came from a crap primary and found that the senior school was really patient and helpful as she got used to what was expected- correct uniform, completing assignments on time and up to standard, polite behaviour to teachers, revision timetabling and organisation. "
The implication that kids from state schools have worse behaviour (eg rudeness to teachers being normal, apparently) 
and are unused to completing assignments on time, lack organisational skills etc etc is based on no evidence at all and entirely contrary to my and my dcs' experience of state schools.
I can only assume that she has no knowkledge of state schools and this is based on watching Grange Hill or something.
As I have stated elsewhere, i think how well a child does at school has a lot more to do with home environment - parents who encourage and nurture their children will have children who do well at school, whether private or state.
I should also add that I came top in the entrance exam for HBS in English with no tutoring at all and FROM A STATE SCHOOL. Shock horror. I had a family who read a lot with high expectations and lots of books. That's all.
And no, we didn't stand up for teachers at HBS and no, I had no problems with 'organisation' either, thank you very much. Nor was I rude to the teachers.
I find horsemadmom's posts insufferably smug. Maybe that's what private schools do for you? Glad my kids are going state all the way...