On the outskirts of the northern city of Aleppo, the teachers just stayed home. The schools had been transformed into shelters for residents displaced by fighting, and in any case, one teacher said, there were more “more pressing concerns” than school.

Other schools had been taken over by rebel fighters, and throughout Syria, more than 2,000 school buildings had been destroyed or damaged in the war.

In an attempt to project calm in the midst of relentless violence, Syria’s Education Ministry ordered schools to open this week. Instead of calm, however, the schools reflected what had happened in the rest of the country during the summer: the fighting had grown worse, the routines of daily life more dangerous and education had become one more casualty of the unrest.

On Sunday, the education minister said that more than five million Syrian students had returned so far. But certainly tens of thousands, if not more, stayed away. Teachers and parents said that educators and students were too scared to return, or unable to, since the schools themselves were occupied, destroyed or inaccessible.

“The Syrian government promised that everything would be O.K., that they will finish the ‘criminal gangs’ before the beginning of the educational year,” said a teacher at a school in a Damascus refugee camp, using a term the government uses to describe its opponents.

“What happened is the opposite,” she said. The fighting grew worse and rolled through the neighborhood and surrounding areas, sending more and more families to shelter in the schools.

Last week, Unicef, citing government estimates, said that of the country’s 22,000 schools, at least 10 percent were damaged, destroyed or occupied by displaced families. In Homs, parents said that classes had started in only a few schools; in one private school, the families living there simply moved to an upper floor. In the Damascus suburb of Barza, one or two schools took students in shifts, to make up for all the schools that were closed.

Different challenges faced Syrians who had fled the country, including to Lebanon, where officials are struggling with a vexing issue: how to teach Syrian students, accustomed to classes in Arabic, in Lebanese schools where science and math classes are taught in English or French.

“When you ask young people about school, they say they’re afraid of the language,” said Soha Boustani, a spokeswoman for Unicef. Last year, she said, the dropout rate for seventh-, eighth- and ninth-grade Syrian students in Lebanese schools was 70 percent, with the language barriers being a major cause.

Syrian students also face discrimination, from Lebanese teachers and students, and resentment from local residents in impoverished parts of the country where the school system is already overburdened.

The United Nations envoy to Syria, Lakhdar Brahimi, visited Syrian refugee camps in Turkey and Jordan on Tuesday, and was quickly given a taste of the anger brewing among the exiles. In the Zaatari camp, near Jordan’s border with Syria, refugees angered that Mr. Brahimi had met with President Bashar al-Assad of Syria chanted, “By seeing Bashar, you’ve extended his life,” according to The Associated Press. As Mr. Brahimi’s entourage left the camp, teenagers pelted its cars with rocks.

The problems for many of the children start even before they register for school. “Some of them have seen dead bodies,” said Miled Abou Jaoude, the emergency coordinator for Save the Children in Beirut. “There is a fear of warplanes. Some families are living in one room, with the father unemployed, which can create domestic violence.”

Aid officials said that the Lebanese government recently directed the schools to accept the Syrian students. The United Nations Refugee Agency and nongovernmental groups are trying to rehabilitate schools to prepare them for more students, especially in low-income areas where repairs were badly needed.

Schools in Syria face a much steeper challenge. In Qaboun, an opposition stronghold outside Damascus that has had fierce fighting, a teacher said his school opened under orders from the Education Ministry: teachers were told to show up, whether the students came or not.

“They wanted to show the situation is as normal as any year,” said the teacher, who, like others, requested anonymity because he was not authorized to speak to the news media.

About 100 students returned Sunday, when classes began, to a school where there were once 50 students in each classroom. “Most of the families left Qaboun,” the teacher said, adding that many of his colleagues had not shown up for work because they lived in other areas besieged by violence.

At a school in the Yarmouk Palestinian refugee camp, a 13-year-old boy scolded administrators for planning to remove displaced families to comply with the order to open schools, a teacher there said on Tuesday. “To be honest, I cried when I heard those words,” the teacher said.

The crisis has not spared the country’s elites, including government officials who used to send their children to private and international schools outside of Damascus.

“I decided to send my son to the state-run school instead,” one father said. “I think that this year, Syrian students will not get a good education.”