I suspect my DC's school has more than its fair share of pushy 'child centric' parents, but thankfully the children are in the main mannerable and well-behaved.
I have been on many school trips with the children and members of the public often complement them on their behaviour, which is always nice.
I wonder whether the small class sizes make a difference - perhpas less crowd control?
My DCs are more than capable of having their moments - but thankfully seem to have been born with an innate respect of authority. I would love to think it was my fantastic parenting but I rather think it is just in their nature to be that way.
I do have, what I consider to be, a professional relationship with school though. I am paying for a service and I expect that service to be of a consistently good quality. I don't duck the difficult conversations, but I am unfailingly polite in my dealings with teachers and other staff. I make sure they know when I think they are doing a great job, which is the overwhelming majority of the time, and equally let them know when I am slightly dissapointed!
I think the problem with some parents, is that they have never learned how to secure a positive outcome to a situation without being aggresive, which as all of us in service provision know, is the ultimate turn off and guaranteed to lead to defensiveness!