Check the Ofsted reports on the school of your choice, forget other peoples prejudices, and decide what you believe is best for your children.
The comments ' it didn't do me any harm' can only cite the argument from one side, if they had attended a different school their comment would the same.
if there is a option on the number of schoola within easy reach, check them all and speak to parents.
The important thing, now, is specialisation of schools, if your children want IT studies, sending them to an art based specialisation defeats the object.
What are their ambitions, which school would best serve that ambition?
The comments ' it didn't do me any harm' can only cite the argument from one side, if they had attended a different school their comment would the same.
if there is a option on the number of schoola within easy reach, check them all and speak to parents.
The important thing, now, is specialisation of schools, if your children want IT studies, sending them to an art based specialisation defeats the object.
What are their ambitions, which school would best serve that ambition?
Anyways rant aside good luck its a hard one init! 
. But in re: to private schools being a nasty manifestation of looking after one's own and damning the rest, I think you said everything very eloquently.