A. Selection Bias-Students attend schools that are within a district. Higher-income children can achieve more than low-income children because their families can afford to live in a more affluent neighborhood and access better schools.

B. Reverse Causality-There can be a preexisting difference between the quality of school districts, which can cause people more likely to choose a neighborhood with a good school distinct. This can cause a cyclical relationship because income segregation leads to gaps in achievement, which leads to gaps in income; the poor stay poor, and the rich stay rich.

C.Cofounders-Income inequality increases income segregation, which can be due to racial disparities.