It’s going to be screen time all the time for kindergartners and graduate students alike. Teachers are threatening strikes. And students are already coming home with covid-19, the disease that has upended American education.

The 2020-2021 school year has dawned and it’s more chaotic than any before.

Plans are changing so fast that students and parents can hardly keep up. Districts that spent all summer planning hybrid systems, in which children would be in school part of the week, ditched them as coronavirus cases surged. Universities changed their teaching models, their start dates and their rules for housing, all with scant notice.

And many districts and col­leges have yet to make final decisions, even now, with the fall term already underway in some parts of the country.

“Plans are changing right up till the moment that schools open,” said Michael Casserly, executive director of Great City Schools, a lobbying group for large districts.

Chicago Public Schools announced last week that it would begin the year online, after planning a hybrid system. Districts across the country have pushed back their opening dates. Last week, the first week of school in Georgia’s Cherokee County School District, administrators sent 14 letters to parents, each disclosing new coronavirus cases. That included 13 students, ­ranging from first to 12th grades, and a few teachers. More than 300 students who had been in contact with them were directed to self-isolate for 14 days.

“Our parents wanted a choice for their children, and we delivered — it is not perfect, and we all know that, but perfection is not possible in a pandemic,” Superintendent Brian V. ­Hightower said in a message to the community on Friday.

Another Georgia high school, in Paulding County, drew national attention after students posted pictures and video of their peers walking without masks in tightly packed hallways. Now, six students and three staff members there have tested positive for the virus, according to a letter sent to parents over the weekend. And on Sunday, the superintendent said the school would go online only for Monday and Tuesday and would announce plans beyond that on Tuesday evening.

Last week, Johns Hopkins University changed its mind and said classes would be fully online, discouraging even those who had signed leases from returning to Baltimore. Students at Washington University in St. Louis faced the opposite problem when the school said on ­July 31 that all dorm rooms would be converted to singles, leaving juniors and seniors scrambling to find housing at the last minute.

In Congress, talks over a pandemic relief package collapsed last week, leaving no clear path to providing schools with funding that lawmakers in both parties agree is urgently needed.

“We knew how to close schools,” said Annette C. Anderson, an assistant professor of education and deputy director of the Center for Safe and Healthy Schools at Johns HopkinsUniversity. “But we have no idea how to properly reopen schools.”

The result of this chaos is uncertainty for students and their parents, with profound ramifications for health, learning, emotional development and economics in schools that open and those that don’t.

Of the 20 largest K-12 districts, 17 plan to begin the year fully remote. The big outlier is New York City, by far the nation’s largest district, which plans a hybrid system and has withstood intense pressure from teachers and others to reverse course.

On Friday, New York Gov. Andrew M. Cuomo (D) gave the state’s 732 school districts the go-ahead to open in person if they like, as long as the state’s low coronavirus infection rates stay low.

Across the country, school districts have wildly different plans based on their geography, infection rates and partisanship.

Four percent of rural districts and 21 percent of suburban districts have announced fully remote plans, compared to 55 percent of urban systems, according to a study of 477 districts chosen as a representative national sample by the Center on Reinventing Public Education at the University of Washington at Bothell.

Robin Lake, the center’s director, also reviewed parent surveys from districts across the country and was struck by how divergent views are.

“Some are saying they are terrified,” she said. “Others are saying, ‘I think this whole covid thing is a farce.’ ”

Like so much in the United States, decisions appear to be falling along partisan lines, with schools in Republican areas far more likely to open than those in Democratic communities.

Polling shows Republicans are far more likely than Democrats to say going back into school buildings is safe. And an examination of district plans compiled by Education Week suggests that campuses are more likely to be open in conservative communities than in liberal ones.

Education Week’s database includes 153 districts in states won by Hillary Clinton in 2016. Of them, 67 percent plan fully remote learning this fall.

Of the 307 districts in states won by President Trump in 2016, 58 percent plan to hold fully or partly in-person classes.

Some of the divide may trace to the fact that rural areas tend to lean more Republican and in some cases have fewer coronavirus cases. But the overall trend worries Daniel A. Domenech, executive director of AASA, The School Superintendents Association.

“It’s a very dangerous and explosive situation, and unfortunately people are more inclined to follow their political bent than to do what is safe for their own families and their own children,” he said.

Trump and his allies have repeatedly pushed districts to open, noting the importance of in-person education for students’ academic and social emotional growth, as well as for parents’ ability to work. Some administrators and the parents they serve seem to be listening.

In Washington County, Utah, for instance, schools were accommodating the desires of a very conservative community when they opted to open for full-time, in-person school. School begins there this week.

“As restrictions lifted, we felt — and the community felt — that would be in the best interest of students to get them back on as normal a schedule as possible,” said Steven Dunham, director of communications for the district.

“We are trying to put into place every safety precaution we can,” Dunham said. “We are also trying to fulfill the requests of the parents in this community.”

The district is requiring students and staff members to wear masks, as ordered by Utah Gov. Gary R. Herbert (R). But Dunham said that “a significant number of parents” have asked the school board to defy the order, something the board has declined to do.

The pressures in more liberal communities often cut the other way, with teachers unions saying it is not safe to reopen campuses.

The American Federation of Teachers passed a resolution endorsing actions including strikes to protest any orders to return to classrooms, and teachers in New York City have threatened to walk out over the issue. The newly installed president of the National Education Association said she, too, supports strikes if needed to get the attention of decision-makers.

“Our members are looking at every option that they have in their toolbox to get those in charge to listen to them when they say their schools are not safe,” NEA President-elect Becky ­Pringle said in an interview. In her inaugural speech, she promised financial help to any affiliate that concludes its reopening plan is not safe for teachers.

Pressure to keep schools open has been intense in Texas and Florida, two states where Republican governors ordered them open and then backed off as infections continued to climb.

The administration of Texas Gov. Greg Abbott (R) said in July that all schools must reopen. Then it said districts could operate remotely for the first three weeks. Then it extended that for several more weeks. Local health departments stepped in to bar some districts from opening. A few days ago, Abbott said the decision was up to local school officials.

John Kuhn, superintendent of the 3,300-student Mineral Wells Independent School District, said he’s trying to follow the state’s orders.

“But it’s not easy,” he said. “It keeps changing.”

Kuhn said he has decided to open schools for students who want to come, but he is encouraging parents to keep their children home so there will be fewer in the classroom and social distancing will be easier. School starts there next week.

Florida Gov. Ron DeSantis (R) also ordered all districts open, then later retreated, saying remote learning would be all right where coronavirus rates are highest. On Friday, he made clear that not all districts would be granted that dispensation, telling Orlando’s News 6 that he was concerned that Hillsborough County, which includes Tampa, plans to stay remote.

“The law requires you to offer a certain amount of in-person instruction,” DeSantis said, referring to his executive order. “I’m concerned about it.”

For colleges and universities, the tumult of campus closures in March gave way to the chaos of planning for reopening under volatile and unprecedented conditions. Some are bringing back most of their students. Others are bringing only certain groups — freshmen, for instance. Still others are telling students it’s best to stay away for the fall. Many international students cannot get visas to travel to the United States, and others who are here are dependent on colleges for emergency housing.

No matter where they are living, students are resigned to a course catalogue with a heavy dose of online learning. Classes might be fully online or hybrid, limiting face-to-face contact with faculty members.

Dorm rooms, by default, will become classrooms. Harvard University is inviting freshmen and select others to live on campus, but all of its undergraduate teaching will be online.

Like their K-12 counterparts, many colleges face pressure from their faculties to shift to remote learning. More than 350 faculty members at the University of Iowa signed a petition demanding that classes be all online. There was similar pushback from faculty members at the Georgia Institute of Technology.

As of last week, nearly 30 percent of 3,000 institutions planned to be fully or primarily online and about 24 percent were fully or mostly in person, according to an examination by the Chronicle of Higher Education and Davidson College.

The review found that 16 percent planned a mix of approaches and 26 percent had not yet decided.

Much remains in flux. The University of Virginia had announced in June that students would be invited to campus for classes starting on Aug. 25. They would live in residence halls under a strict public health regimen that includes assigned sinks and showers. Now U-Va. says the undergraduate arrival will be delayed because of the surge in virus cases, and face-to-face teaching will not start until after Labor Day.

Some plans fell apart weeks after they were announced. The University of Southern California in July reversed course on an aggressive reopening, and then last week ratcheted back again to almost entirely remote. Georgetown, George Washington and American universities, all in the nation’s capital, took similar zigzag paths toward remote openings.

At American, a private university with about 14,000 students, officials had painstakingly pieced together a plan to house about 2,300 students on campus in single dorm rooms and teach through a blend of in-person and online methods. The school calculated classroom capacity under a social distancing model, taking into account whether seats were fixed or mobile. It tracked how many faculty members had health concerns and who could teach in person and when. Assembling the course schedule, said AU President Sylvia M. Burwell, was like solving a Rubik’s Cube.

By the end of July, that plan went out the window.

“I’m disappointed,” Burwell said. “We’re all disappointed.”

Burwell, who was health and human services secretary during the Obama administration, said the trajectory of the pandemic now dictates caution. She said she spent weeks gathering facts and enduring many sleepless nights before deciding to shift course. Now she’s pledging to make it work.

In California, the leader of the largest public university system in the country saw this moment coming months ago. Timothy P. White, chancellor of the 482,000-student California State University System, had announced on May 12 that most fall instruction on its 23 campuses would be remote. It was at the time a shocking statement of higher education’s vulnerability to the virus.

Now White says he is glad he staked out a radical position. It gave his faculty ample time to prepare and freedom to innovate. “It allowed a different mind-set,” he said. The attitude: “Now, let’s get to work and figure out how to do it great.”