I have kind of a different take that you might appreciate. I, too, grew up in a very high pressure educational area (DC) and ended up going out of state for college. It happened to be a private school, but I could count the number of people that I knew on one hand and lived in hall dorm with a stranger. My husband grew up in the midwest and went to state school. He and his high school best friends were roommates all 4 years. They basically merged with 2 other groups of high school friends in college and that is his social circle.

My two greatest takeaways from our experiences:
1. It was extremely eye opening for me as an 18 year old to meet people from all different parts of the country and to go to school in a different part of the country. Hugely. And yeah I learned a lot in school, but I definitely also learned a lot from those experiences. I don’t think I was particularly sheltered before, but it definitely made me more open-minded and helped me to wrap my mind around the fact that others have way different upbringings than me. I’d go so far as to say it made me who I am. My husband’s social circle that I’ve become close with over the years… not so much. It really smacks you in the face that almost all of them have never lived more than 2 hours from where they were born. And I have that same observation of my friends from the DC area that stayed local, too. Not quite to the same extent only because bigger cities bring a bit more diversity generally, but you get the picture. This convinced me that I really want my kids to go out of state for school if it’s feasible.
2. I remember first meeting my husband’s friends in our early/mid twenties. This is anecdotal evidence but their social skills were crazy stunted. They had basically no ability to have a conversation with someone that was a stranger, much less someone who didn’t grow up in the same area as them or understand their references (for example they would sneer if I didn’t know what a grocery store was. Yes, they didn’t even understand that grocery stores are different in different parts of the country..). It crossed being uncomfortable into being extremely rude, honestly. It was kind of shocking to me. Over the years as they got more mature and started meeting more people at work, etc. that were presumable not from the 50 mile radius of their hometowns, it got a bit better. But this made me determined that my kid is living with a stranger when they go to college. They might have gone to a state school 10 times the size of my school, but I don’t think they are bad people- they just missed that lesson of being forced to get to know a stranger.

In this case I happened to go to to private school and they happened to go to public school. I really don’t think that was the huge determining factor. I think it’s easy to slap a label on the “big city” or “private school” people as more snooty and assume that the more folksy public school folks are just salt of the earth and how *real* Americans live. But truly in my experience I’ve found there’s more to it than that.

Also – as someone who went to a small prestigious school that is no where near where i now live: 1) you don’t know where your kids will decide to ultimately live and 2) large state schools have incredibly strong alumni networks. I’m often times jealous of the strength of the alumni networks of friends and colleagues that went to larger but technically “less prestigious” schools.