President Rene Preval, who has made several visits to the disaster site, blamed continual government turnover and a lack of respect for the law for the deadly collapse at the College La Promesse.
"There is a code already, but they don't follow it. What we need is political stability," Preval told The Associated Press.
Stephen Benoit, Petionville's representative in Parliament, called the tragedy a "golden occasion to address this anarchic construction."
"We need a new city. This is one catastrophe - but we have many more to come," said Benoit, who proposed freezing government spending next year on items such as cars and official travel to help finance construction of sturdy settlements.
Benoit estimated that as many as 2 million Haitians live in ramshackle slums across the Caribbean nation of 9 million. Haiti's mountainsides are blanketed with squalid homes, shabby churches and poorly constructed schools like the one that tumbled down Friday.
Rescuers including a U.S. crew from Fairfax County, Virginia, and French firefighters from Martinique continued searching for survivors and the dead for a third day Sunday, using pole-mounted digital cameras and cutting through concrete with saws. They were aided by an eight-person military team from the U.S. Southern Command.
But anger boiled over as thousands of Haitians looked on in the blazing sun, with the stench of rotting bodies beginning to rise from the rubble.
About 100 men rushed the unstable pile at one point, hammering at the debris and trying to pull down a massive concrete slab that firefighters worry could trigger a second collapse.
Thousands cheered them on, chanting, "We don't need money to do the work!" Rumors have circulated that the international rescuers were working slowly to inflate their wages.
Baton-swinging Haitian police and U.N. peacekeepers in riot gear drove the men away, only for them to return and throw rocks.
Tensions eased after authorities let several dozen locals help clear rubble under U.N. supervision.
"Everybody is frustrated. We smell the bodies," said 25-year-old Emmane Petitehomme.
Some have reported hearing voices from the pile or receiving cell phone calls from trapped survivors. Rescuers say they investigated those claims but could not confirm them.
By Sunday evening, rescuers continued to chip away at an unsteady wall of concrete that kept areas off limits where more crushed victims were expected to be unearthed.
The school's owner and builder, Protestant preacher Fortin Augustin, was arrested late Saturday on charges of involuntary manslaughter, police spokesman Garry Desrosier said.
Neighbors said they have long complained that the three-story school building was unsafe, and people living nearby have been trying to sell their homes ever since a section of it collapsed eight years ago.
"You can see that some sections just have one iron (reinforcing) bar. That's not enough to hold it," said 55-year-old Notez Pierre-Louis, whose children used to attend the school. "I said all the time, one day this is going to fall on my house."
Kaje Pierre, a 27-year-old food vendor who lives up the street, said he fears for the rest of the neighborhood, where many homes are worth about $9,000 - several years' salary for most Haitian workers.
"I'm worried these other houses might fall because they're too close to the ravine," he said. "But we have no choice. This is what you can get for the money we have."
The tragedy has elicited shock and sadness around the world.
Pope Benedict XVI sent a message expressing his condolences, Vatican Radio said Sunday.
In addition to the 88 students and adults found dead, at least 150 people have been treated for injuries in the collapse.
Roughly 500 students typically crowded into the hillside school, but it is not known how many were there when it crumpled on Friday around 10 a.m. local time, said civil protection coordinator Nadia Lochard.
Haiti, the poorest country in the Western Hemisphere, has struggled this year to recover from riots over rising food prices and a string of hurricanes and tropical storms that killed nearly 800 people.
