To be clear I grew up fairly poor myself with no support system, but not that bad with violence, just trailer park poor, you can tell smart children at a very young age, kindergarten it will be obvious if a student is mathematically gifted(for whatever that is worth, it is certainly not the end all be all indicator of future success).
my point is that MIT will have a higher percentage of mathematically gifted students, because it isn't something that can be prepped for.
I guess I would be curious on how much a difference it really is , if you could completely control for environment, but even then the difference still exists.