I agree with those above who have said that there may be a combinations of classism and inferiority going on.
quote: For now things are cool, kids that young don't care.
My .02 cents. You seem to be committed to sending your daughter through school with these kids. You also seem to be very grounded in the way you are raising them. But your daughter at some time will certainly see the wealth surrounding some of these other kids. I only bring this up because you mentioned she's too young to notice and I'm sure you are correct. But you may want to be prepared for when she realizes you can't play by the same rules as some of the other parents.
Kids can be awfully mean to each other. Show your daughter the importance of working hard (many of the rich kids won't be) and the meaning of a dollar. If she has a solid basis, she's more likely to inherit your thick skin and healthy attitude.
I don't want to step on your toes and tell you about your raising kids. I have none. But I've seen how kids who have can be really mean to those who have even a little less. Kids might not understand class seperation, but they get have vs. have-not. And the haves, often in conjunction with *sshole parents, put it on display.
I'd just have some plan of action for when she starts to perceive differences. Think about it now, so you'll be ready. Whether its a talk or an allowance, whatever you come up with.
Finally, good luck to you. You can be upset, but you can't lose your cool, so you did well. Remember, if you stay put (and I hear Colorado is nice), that the same group of parents you were with the other nite you'll see for the next 12 odd years or so!