Val-I am on my iPad so I am not great with pasting and copying so sorry if it gets muddled smile.
I am not great at math but I know how to teach my kids how to learn. I am also resourceful and will find ways to help them when I am out of my comfort zone. I know I will get there sooner vs later with ds9. Yes I am well educated - formally and informally( parents) so I have a leg up on understanding how to find the resources- today Khan academy and others gives everyone access to additional coaching.
I also did not start reading in utero- however I know numbers of friends who did. I did read to them every day after they were born and start identifying numbers, letters, colors etc.... As early as I thought was right for each kid.

I agree that lower income pass on their education traditions too- that has a great impact on what happens to the kids. I understand what you are saying about how can they help their kids with work they don't understand- but the school is not responsible- if they get extra guidance then it is wonderful and an extra not an expectation. Most communities have options to get the extra help- but you have to want it.
There are a number of stories we have all heard about that demonstrates that kids can grow out of the lower economic strata but it generally has a background of a parent who was willing to do whatever it took to get the best for their kid. They understand the culture of educating their kids outside of the traditional basic education.