It depends on the school, of course.
If "they" happen to be a school filled with well-off kids from two-parent families, they generally do great on the tests.
And if "they" happen to be a school filled with poor kids from a place near the street named for MLK, they'll almost always do poorly.
Testing can't deal with that kind of difference.
Testing shows that difference. Whatever dealing there is lies beyond the purpose of tests. What to do about 'high blood pressure' is not the purpose of the test.
Yes, children may have it hard if their parents [parent] are not learning role models or have split up. I doubt tests or educators can be of much help. I don't think it would be socially acceptable to put them in different schools for different education. Sort of separate but unequal.