On what was supposed to be the first day of school in some Texas districts, the state with the nation’s second-largest K-12 student population was in educational crisis Monday, with hundreds of thousands of families reeling from the effects of Hurricane Harvey. Teachers, students and parents were unsure when classes would be in session, and who, exactly, would be reporting to which schools, when opening bells finally ring.

More than 160 Texas public school districts and 30 charter schools were closed, according to an initial count. The upheaval threatened schools across the state, even ones unaffected by the storm itself, as families flee to San Antonio, Austin, Dallas and other cities with school systems already dealing with their own financial and academic challenges.

At an Austin sports arena being used as a shelter, Shirelle Franklin, 31, sat on a cot near her four children, three of whom attend schools in the Coastal Plains town of Victoria, Tex. Ms. Franklin said her family’s apartment complex sustained extensive damage, so she was unsure when she would be able to return home. Classes at district schools in Victoria have been postponed until next week.

The family fled abruptly with little time to gather school materials. Ms. Franklin’s 14-year old son, Noey Alvarez Jr., worried about falling behind academically. “I don’t like to miss out and having to catch up,” he said.

In Houston, Arelis Vallecilla, Chad Stearns and their six school-age children were preparing to spend the night in a shelter at the George R. Brown Convention Center.

“We lost everything,” Ms. Vallecilla, 38, said. Floodwaters destroyed their home, their truck and virtually all their possessions, including nearly $900 in new school uniforms and shoes.

Her children had spent the day playing checkers instead of learning in a classroom. They had been looking forward to the start of the school year this week, Ms. Vallecilla added, but their studies were now in limbo.

The situation recalled one that many New Orleans residents faced in 2005, when Hurricane Katrina severely damaged most public school buildings and incited sweeping education reform efforts that remain controversial 12 years later. At that time, more than 100,000 New Orleans residents fled to the Houston area, whose schools absorbed over 20,000 displaced students. Many of those children struggled academically and socially.

Now the Houston region, among the hardest hit by Harvey, may lose some of its own students.

The closed districts in Texas stretched some 300 miles along the Gulf Coast, from Corpus Christi, close to where Harvey made landfall, to as far north as Beaumont. Inland schools, too, were closed on Monday, including many east of Austin.

A number of local districts, including Houston’s, the state’s largest and the seventh-largest district in the nation, said they hoped that Tuesday, Sept. 5, would be the first day of class. But local and state officials acknowledged that they could not predict exactly when buildings would be safe to re-enter and roads to schools would be passable.

“I don’t think we know for sure when everybody will be back,” said Lauren Callahan, a spokeswoman with the Texas Education Agency. “It’s too early to tell how many schools have sustained physical damage.”

Doug Harris, director of the Education Research Alliance for New Orleans at Tulane University, is an expert on how school systems react to natural disasters. It will be important, he said, for the State of Texas and local schools to be flexible in terms of where displaced or homeless students enroll, and to make sure that struggling families — including Texas’ many undocumented immigrants — are comfortable turning to public schools for help.

“The highest priority has to be getting students back to school,” Mr. Harris said. “And counseling. There was a lot of trauma after Katrina.”

Richard Carranza, superintendent of the Houston Independent School District, estimated that as of Monday afternoon, 35 of the city’s school buildings — more than 10 percent of the total — had power failures or had flooded. With rain forecast for days, the damage could get much worse.

“It’s a Houston-wide tragedy, so everybody is being impacted, our employees and our families,” Mr. Carranza said. “We’ve been really transparent that weather conditions and, quite frankly, city infrastructure are going to determine whether we are going to safely be able to open” on Sept. 5, as planned.

Charter schools, which educate about a fifth of the city’s public school students, were also affected. Harmony Public Schools, which operates 15 charter schools in the Houston metropolitan area, said that one of its campuses sustained major flood damage. At KIPP Houston, which operates 28 charter schools serving 14,000 students, officials said they were still unable to access many of their buildings to make a full damage assessment. About 40 KIPP Houston families had lost their homes and many had been evacuated.

Dawn Kotecki, a teacher at Cesar Chavez High School in southeast Houston, was setting up her social studies classroom with a group of student volunteers on Friday morning, when the principal directed everyone to evacuate the building within minutes — the hurricane was coming, and the school year would not begin as expected.

After Harvey, Chavez students and teachers will face a host of challenges. A bayou behind the building overflowed and reached school grounds, Ms. Kotecki said. And an unknown number of students and teachers were evacuated or had lost their homes.

Ms. Kotecki, who was safe at her own home in suburban Pasadena, Tex., said she was raising money and collecting clothing, personal hygiene items and school supplies via Facebook. When Chavez opens for the year, “we will do a daily check-in” with students, she said. “Is everything O.K. at home? Did you get a good night’s rest? Did you have a good breakfast? If not, we will make sure that they do.”

The Houston school district serves approximately 215,000 students, more than three-quarters of whom are from low-income families. Harvey made landfall at a politically sensitive time for the city’s schools. In early August, the state informed the school board that the district was at risk of a state takeover, because of a 2015 law that targets districts with persistently underperforming schools.

Those 15 struggling schools are clustered in the city’s poorest neighborhoods, and two to three of their buildings are among those with serious physical damage, according to Mr. Carranza, the superintendent.

When Hurricane Katrina hit New Orleans in 2005, four-fifths of the city’s school buildings flooded, resulting in an estimated $600 to $800 million in damage. It took most schools more than four months to reopen, according to Mr. Harris of the Education Research Alliance for New Orleans, and even middle-class students were reclassified as homeless, as families struggled to rebuild or find new homes.

That physical devastation remade education policy in the city. Louisiana’s Recovery School District law, which dated back to 2003, allowed the state to take over the district, leading to the dismissal of thousands of teachers and an expansion of the charter school sector.

It is not yet clear if Houston and other Texas school districts have sustained comparable physical damage. Mr. Harris noted that Houston schools are in stronger condition than New Orleans schools were before Katrina: Houston’s buildings were constructed much more recently and are in better shape.

Mr. Carranza, the Houston superintendent, said that after the crisis of Hurricane Harvey passes, the district would resume its work turning around the low-performing schools on the state’s watch list.

In the short term, however, “I haven’t spent a lot of time thinking about” the potential for a state takeover, he said. “We’re in lifesaving mode.”