YANBU, I think you will be OK, but I know where you are coming from.
We live in the states, in a dismal school district. We ended up finding a wonderful, albeit posh, private prep school, that I was afraid to go in an even ask how much the tuition was. While our state as a whole education wise is going into the toilet, this school is wonderful. He is getting such a good education, is being challenged, we couldn't be happier with our choice.
The tuition is Double what we were paying before, (moved cross country) Dh's salary went up, but in reality he doesn't take home much more than he did in our old state. We live on a very modest street, smallest house on the street. Ds has friends that have Two homes, travel to Hawaii on a whim...and this friend has actually turned out to be the most caring, sweet boy I could ever hope my ds to have. We fixed up our house to look really nice, and even had the 'compliment' of one of his friends saying, "Wow your house, is Really nice...since you know, it is a small house!" :) Yes it can exist child!
Ds has friends that can only afford to go there because his parents teach there and he couldn't care less. Most of the parents - really - are rolling in it, but it has little effect on ds. He knows the scoop, he knows we put our money were we feel it best utilised, he knows that he's not going going to Italy every year with some students, or his spring break won't be filled with going on posh vacations every year. We do what we can, when we can, and he totally gets it and is very practical about it. We have his friend's parents at our house, which is a tiny and dated compared to what they have, (and what we used to have in our old state) but it's homey, warm, bright and clean.
Now I'm not going to lie. At our other school, I have a friend in a similar situation. She has a dd, and one of the mom's of her dd's friends tries to keep the girls apart, and my friend is convinced (since the girls get alone just fine...my friend's girl is like a little mouse and wouldn't offend anyone!) that the mom tries to encourage her daughter to spend more time with other girls - but not just any other girls - the ones whose parents have money, because well, they might afford to offer her daughter more. So it definitely Can exist. But those cases are few and far between. If the school does an excellent job of instilling good values (as we as parents do) the children will grow up Knowing which people they want to be friends with regardless of what their parents say!
Sorry this is a novel. I think you will be totally fine. I find it easiest when laid out very business like when we don't go on posh vacations all the time (we do once in awhile) and if your ds is anything like mine, he will grow to be appreciative of what we do provide for them, and not just take it as that is the way the whole world lives.
I myself, feel I have much more in common with the people that actually clean the school, and I'm being honest here! The Parents can be the intimidating ones, but I look for friends outside my child's friend's parents and classmates.