(a) There is nothing "wrong" with being poor. I spent all of my childhood and several years of adulthood in the so-called, "Bottom Quintile" of household incomes in the U.S. And now I'm in the top quintile, not that that is any great accomplishment.
(b) If you want to find the reason why there are so many poor children in our schools (regardless of geography), the main reasons are the empty promises of the Welfare State.
Back when "Middle Class Values" prevailed in this country, most people tried to control the size of their families and didn't bring children into the world unless they had the resources to support them. (Roman Catholic teachings nothwithstanding). If you were NOT MARRIED, or were married and hopelessly poor, you took precautions not to have children, or at least to minimize the number of children, until your economic prospects were better.
But now we have the Welfare State, that promises perpetual food, shelter, and income if you pop out a few kids and create a "household." And it encourages you to blame your poverty on the bigotry and greed of others.
If the worst racist bastard on the planet had wanted, in 1965, to create a situation that would ensure the perpetual poverty of the majority of the descendants of American slaves, he could have never dreamed up a program as destructive as the American "welfare" system.
And yet, more than a trillion dollars into it, the creators of it are still convinced of its success, and WONDER WHY most African Americans are still living in poverty. And they talk about "Red States" and "Blue States" when addressing the poverty of the progeny of the Welfare State. What rubbish.
If you made this up, nobody would believe you.