what
@chulent said is true, the more schools that become necessary due to community growth the more specificity there is in each school. And sadly, the more in town the city becomes.
For example, LA is well known for the Chabad, Chassideishe and general community being very well integrated. However, consider that when my wife was in HS there was only one Bais Yaakov. Over the past 15 years they have opened a Chabad Bais Yaakov and a Chassideshe Bais Yaakov. They also opened a second, less academic, Bais Yaakov.
Will my children feel the same integration that we did?
Consider further, that in my children's K-8, mainstream school (there is also a Chabad school, and a chassideshe school which opened in the last two decades) there is still a broad mix of families, from super yeshivish to TV in the living room. (I'd guess that at this point 99% of the parent body cover hair etc.) Most are squarely in the middle. However, the influences that I have trouble with come clearly from the right, not from the more modern side. Because if the Kleins, go to Bermuda for Pesach, or the Friedman's mommy listens to non jewish music, I can explain that to my children, and show how we have such a awesome and beautiful Torahdige life. However, when Rabbi A.'s daughter has a brand new wardrobe every YT, and my son comes home from Rabbi B.'s home, after playing with his son and asking to continue the video, because they 'have a computer that hangs on the wall in the playroom' and were watching LizardLand or whatever, and Rabbi A. and Rabbi B. are considered by all to be chashuva klei kodesh, and Rabbi C.'s wife has a DVD gemach of kosher movies, which we don't like our kids to watch, I sort of feel like I'm better off with my kids having the more modernishe friends.
#stepsoffsoapbox (but reserves the right to step back on)