At Wheatley, a high school that is northeast of downtown Houston, the principal, Shirley A. Rose-Gilliam, greeted upperclassmen by name and directed traffic in the halls. She said she had been unsure how many students to expect. In the end, she was relieved. More students were at school on Monday, she said, than on any first day in her four-year tenure here.

A drop-off in enrollment could have led to a decrease in state funding and potential reassignment for teachers at a time when the school is already under scrutiny. Wheatley, whose student body is about half Hispanic, half African-American and 70 percent low-income, is in its sixth year with “improvement required” status. If test scores and graduation rates do not go up, the school could be shut down by the state.

“We’re working to get the scores where they need to get to, but at the same time, it’s not necessarily about scores,” Dr. Rose-Gilliam said. She said she was encouraging teachers to discuss the flooding in their classes, and urged her staff to help displaced students access counseling, clothing and even toiletries.

In the aftermath of Hurricane Katrina 12 years ago, most New Orleans public schools remained closed for more than four months. The State of Louisiana took over most New Orleans public schools, instituting changes that created the nation’s first so-called “portfolio” school district, in which the majority of schools are independently managed charter schools. Gains in test scores and the high school graduation rate followed, yet the overhaul started a fierce, ongoing debate about how to balance education reform efforts with community control of schools. Thousands of experienced African-American educators with deep roots in New Orleans were replaced by a movement of largely young, white teachers from outside.