On the day the 6.4-magnitude earthquake shook Puerto Rico, Agripina Seda School — in the seaside community of Guanica — was empty. Many of the middle school’s 200 students were home, enjoying the final days of a long winter break.

Had they been in class, they may not have made it out alive: Following the earthquake and its aftershocks, part of the three-story school collapsed, each floor pancaking onto the one below.

Parents, teachers and a professional association of structural engineers have expressed concern over the safety of the island’s public schools, many of which bear similarities to the one that collapsed in Guanica — buildings constructed from reinforced concrete. And they have been skeptical that the territory’s government is doing enough to ensure schools are safe.

Puerto Rico has been rattled by a series of earthquakes since December. The strongest struck Jan. 7. But aftershocks continue to shake the island — some nearly as strong as the largest. Guanica was near the quake’s epicenter.

“We are very worried about the condition of the schools,” said Carmen Warren, president of a committee that advocates on behalf of students with special needs. “The schools are not safe.”

By Monday, classes had resumed at 177 of the island’s 865 schools, according to Puerto Rico Education Department spokesman Aniel Bigio. The department hoped to have 228 schools open by week’s end.

For now, the government said it can inspect and repair only schools damaged by the earthquake, not those that might be at risk of collapsing in a future event.

The quake represents the latest challenge for a school system repeatedly tested by catastrophes, including a long-standing financial crisis that led to school closures and, in 2017, Hurricane Maria, which damaged schools and left children out of classes for months.

Between 2006 and 2018, the number of schools in Puerto Rico fell from 1,515 to 855, according to a report by the Center for Puerto Rican Studies at Hunter College. Hundreds of thousands of students left the island during that period, causing school enrollment to tumble by 44 percent.

Educators are bracing to receive children traumatized anew. In some ways, the earthquakes have created more anxiety and fear for children, said Pedro Sanchez, a librarian at Agripina Seda School, because they keep recurring. Many of his students are living in encampamientos — outdoor camps — because their homes are damaged and too dangerous to enter. Sanchez has taken to sleeping on a couch in his front yard because he worries about the condition of his earthquake-damaged home.

His school was damaged by the largest earthquake Jan. 7 and sent hurtling to the ground by aftershocks. Now, a messy pile of concrete slabs lies on the campus.

“Right now,” Sanchez said, “there is a lot of fear of buildings of any kind.”

Structural engineers pin the blame for the collapse in Guanica on a building feature common in school designs on the island. Many schools have lines of windows along the top of outward-facing classroom walls, meaning the weight of upper floors is held by short columns that run in between rows of windows. These structures are more prone to cracking and failing if they are not reinforced.

“When you have seismic motion, you will have a collapse,” said Félix Rivera, president of the Earthquake Commission in the College of Engineers and Surveyors, a Puerto Rican professional association. Rivera said up to 500 schools may have this feature. Many were built before 1987 — the first year that the island had seismic requirements in its building codes.

Carlos Pesquera, a structural engineer and adviser to Gov. Wanda Vázquez Garced, said there is a longer-term plan to retrofit schools that are not up to code. But in the short term, government officials want to get students back to class.

“The goal of the inspection is to determine whether or not a facility was impacted by the recent earthquakes. It’s very focused,” Pesquera said. “We recognize that there are pending issues that need to be addressed . . . because not necessarily all of them are up to code with regard to earthquakes.”

Compounding the fears of parents and teachers is a deep mistrust of the government in the aftermath of a scandal and federal indictments that took out some of the island’s elites.

Gov. Ricardo Rosselló was forced to resign after a leak of chat messages angered islanders. In those chats, Rosselló talked crudely about women and callously about Hurricane Maria victims.

Before that, Rosselló’s education secretary, business executive Julia Keleher, was indicted with five others on charges she steered government contracts toward favored firms. She pleaded not guilty to those charges, and a trial is scheduled for the summer.

This month, Keleher was indicted on further charges that she allowed an apartment developer to use a portion of a public school in exchange for giving her a deal on a luxury apartment. She has not entered a plea on those charges.

Puerto Ricans in recent weeks took to the streets in anger over the discovery of a warehouse filled with unused disaster supplies, including diapers and bottled water.

“There’s no trust whatsoever in the evaluation that the government is performing,” said Mercedes Alvarez, president of the Puerto Rico Federation of Teachers, a teachers union.