According to US News & World Report, great elementary and middle schools educate their students from all socioeconomic backgrounds with the goal of setting them up for success. In turn, their students develop the core competencies in state curricula to best prepare them for high school.
The rankings use the same methodology for all included grade levels. For each state, schools were assessed on their shares of students who were proficient or above proficient in their mathematics and reading/language arts state assessments. Half the formula was the results themselves; the other half was the results in the context of socioeconomic demographics. In other words, the top-ranked schools are all high achieving and have succeeded at educating all their students.