Girls raced up the school steps in their plaid pinafores and backpacks on Tuesday, ponytails tied tight with colorful ribbons. They hugged and squealed and swapped dramatic hurricane stories, eager to catch up after more than a month away.

“We are ready,” Kenia Caraballo Rivera, the principal at the Dr. Francisco Hernández y Gaetan school in San Juan, said with a smile as students stopped to say hello or embrace her.

“And this,” she added, pointing to a beige folding table and chair in the main hallway near the entrance, “is my office.” With no electricity in the school and no windows in her office, Ms. Caraballo works in the hall, where daylight streams in through the front door.

The resumption of classes at the school on Tuesday was a joyous, achingly needed milestone on the plodding path back to normality in Puerto Rico’s newest era: After Maria. But the island’s education system is hardly picking up where it left off before the storm.

Only 98 of the island’s public schools reopened on Tuesday, 9 percent of the total, and the ones that did were in San Juan and Mayagüez, two major cities. Another 112 schools in those areas will open as soon as their final paperwork is turned in.

Few, if any of the reopened schools have generators, or internet access, or air-conditioning. School days have been slashed in half, at least for now. And the students — the ones who have not moved to the mainland — must bring their own water bottles and douse themselves in repellent to fend off the island’s mosquito invasion.

Since most of the students have no electricity at home, either, homework is now out of the question. Many of them lost clothes and furniture to the storm, so uniforms have been made optional. Old-school is an all too literal way to describe classroom work: white boards, markers, flash cards, board games, and the occasional textbook have reappeared.

With more than a month of lost instructional time to make up at the reopened schools, and still more at the ones that have yet to reopen, the curriculum will have to be truncated, focusing strictly on the most important core elements for each grade. And the school calendar will have to be extended, perhaps into next summer.

“In terms of education, we know that it will not be a perfect year, but we need to take the first step,” Julia Keleher, Puerto Rico’s secretary of education, said in a statement on Tuesday. “It’s important to start wherever we can as soon as possible. But, I repeat again, only when it’s safe for the school population.”

Inside Hernández y Gaetan, a public elementary school that serves two poor neighborhoods in San Juan, students buzzed with stories about rising floodwaters, felled trees and soggy furniture. A teacher sat the school’s fifth-grade students in a circle and asked them to share their experiences, if they felt comfortable talking about them. The discussion was part of a larger strategy to incorporate the hurricane into lesson plans, both to help students cope and to help teach subjects like climate change, geography, plant life and the ocean.

Most of the students seized the chance.

“Are you happy to be back?” asked the teacher, Lorimar Morales.

“Well, not so much, because there is no power and it’s hot,” Heidi L. Rojas de Jesus, a talkative 10-year-old, said with a smile as she fanned herself with a piece of paper.

The students rattled off their losses, which were relatively minor compared with harder hit parts of Puerto Rico. Toppled avocado trees. Clothes ruined by rain or floodwaters. A wrecked mattress. A nearly destroyed Sony PlayStation. One student spoke of a dramatic rescue of an older woman whose house filled with water. Many reeled off a litany of grievances about the heat, the darkness and the endless waits in line for money, for gasoline, for bottled water.

“But the funniest thing is that our garbage can floated away in the water,” Heidi said.

Getting even the 98 least-damaged schools reopened was a difficult undertaking in the wake of Hurricane Maria, which roared across the island on Sept. 20 as a Category 4 storm, demolishing houses and buildings, trees and roads, and knocking out power and telecommunications. The power is still out in three-quarters of the island, and about one-third lacks cellphone service. Few homes have working generators.

Each school building had to be inspected by the Army Corps of Engineers and had to have working water before it could reopen. They had to be repaired, disinfected, and scrubbed of mud, mold and rat droppings; much of that work was done by determined teachers. The schools had to be able to feed the students, and there was paperwork to file. As a test run, the schools first opened as community centers to work out the kinks.

Ms. Keleher, the education secretary, said in an interview that so far, 150 of the island’s 1,113 schools have been rated as too badly damaged to reopen; their students will have to be accommodated elsewhere. It was not clear yet how many students have moved to the mainland. The Hernández y Gaetan school counted five.

Teachers have left, too: Islandwide, about 116 have applied for a special sabbatical that ends in January.

Mari Lopez, who teaches English at the Hernández y Gaetan school, may soon join them. As she kept her eye on a downcast little girl who was ordinarily cheerful and lively, Ms. Lopez, 59, said the devastation on the island has been hard to bear, and she misses family members who have gone to the mainland.

“It’s too much,” she said. “I don’t know how long it will take to get the power back on. It never comes.”

About 30 miles away in Humacao, where Maria left lines of concrete poles snapped in half and wrecked big-box stores, teachers at the Lidia Fiol Scarano school are desperate to get back to work. They already know which songs will greet the children; they have chosen what to grow in the garden in the school’s now-barren courtyard. Even the script for the Christmas show, with amusing skits about facets of post-Maria life like washing clothes by hand, is close to finished. All they need is a reopening date, which may still be far-off because of the extensive damage to other area schools.

The day after the hurricane, the principal, Migdalia Torres, and many of the teachers went to the school to take stock. All 19 of the big trees in the courtyard had been toppled, blocking access to the mud-caked classrooms and robbing the school of shade. Ms. Torres went to a local National Guard station and got 22 soldiers to follow her to the school, where everyone donned gloves and masks and got to work chopping, cleaning, wiping up and discarding debris.

Another school in Humacao had been flooded with five feet of water from the ocean and an adjacent lake. Soldiers pitched in there too, helping the school staff rescue a building that had looked like a lost cause. One wing is still in bad structural shape, but the staff is pushing hard to reopen the rest.

“The teachers have been the heroes here,” said Sonia L. Rodriguez Gonzalez, the principal.

Ms. Keleher said she hoped to give Puerto Rico’s long-ailing schools a boost after Hurricane Maria by decentralizing the school system, instituting greater local control and modernizing the curriculum.

The students in San Juan spoke of another transformation: People are being nicer to one another. One boy said that his neighbors had shared their brooms and machetes. A girl said an ambulance driver had said hello to her.

“And my neighbor used to be mean to me,” said Alanis Santiago, 13. “Now that I have a generator, she’s very nice.”