Why does sister superior assume Esperanza lives in the ugly three flats?

Sister Superior assumes Esperanza lives in the "ugly three flats" because of her socioeconomic background and the general stereotypes associated with her neighborhood. The assumption reflects societal biases about poverty and living conditions, suggesting that people from lower-income areas are often judged based on their surroundings rather than their individual circumstances. This highlights the theme of identity and the impact of environment on perception in "The House on Mango Street."