The storm killed at least 1,800 people and displaced about 65,000 students,

So you’re comparing two radically different populations. The key question is who did not return to the system? Most likely those who had fewer roots and less security, no homeownership, no insurance, etc. were more likely to end up in a totally different neighborhood or city. These are factors that correlate highly with success in school.

This would be like getting rid of a cancer ward in a hospital and replacing it with a plastic surgery ward for rich housewives and then noting the death rate at the hospital has radically declined and declaring that the doctors and administration must have gotten much better.