Agricultural yields have doubled; child mortality has dropped by 30 percent; school attendance has shot up and so have test scores, putting one local school second in the area, when it used to be ranked 17th; and cellphone ownership (a telltale sign of prosperity in rural Africa) has increased fourfold.

There is a palpable can-do spirit that infuses the muddy lanes and family compounds walled off by the fruity-smelling lantana bushes. People who have grown bananas for generations are learning to breed catfish, and women who used to be terrified of bees are now lulling them to sleep with smoke and harvesting the honey.

“I used to think, African killer bees, no way,” said Judith Onyango, one of the new honey makers. But now, she added, with visible pride, “I’m an apiarist.”

Sauri was the first of what are now more than 80 Millennium Villages across Africa, a showcase project that was the dream child of Jeffrey D. Sachs, the Harvard-trained, Columbia University economist who runs with an A-list crowd: Bono, both Bills (Clinton and Gates), George Soros, Kofi Annan, Ban Ki-moon and others.

His intent was to show that tightly focused, technology-based and relatively straightforward programs on a number of fronts simultaneously — health care, education, job training — could rapidly lift people out of poverty.

In Sauri, at least, it seems to be working. Some of the goals were literally low-hanging fruit, like teaching banana farmers to rotate their crops. Other programs were more sophisticated, like the battle against malaria, which employs cutting-edge mobile technology against a disease that kills more than one million children each year.

The other day, a community health team in Sauri stooped through the doorway of a home of several sick children, said hello to Grandma and got to work. Within minutes, a health worker had pricked a child, sent a text message with the blood results by cellphone to a computer server overseen by a man named Dixon in a town about an hour away and gotten back these instructions: “Child 81665 OKOTH Patrick m/16m has MALARIA. Please provide 1 tab of Coartem (Act) twice a day for three days.”

These small miracles are happening every day now in Sauri, population 65,000. But the question for Mr. Sachs and his team remains: Is this progress, in development-speak, scalable? In other words, is there a way to take a place like this one and magnify the results by 1,000 times or 10,000 times and wipe out poverty across the developing world?

Hundreds of millions of dollars may hinge on the answer, because African nations and Western donors are closely following the data emerging from the Millennium Villages. Mr. Sachs and his team will publish their midterm review later this year, though influential donors like Mr. Soros are already betting on Mr. Sachs to the tune of several million dollars each year.

Colleagues say Mr. Sachs, 55, has single-handedly done more for foreign aid than just about anybody in recent years. “We need Jeff,” said Nancy Birdsall, president of the Center for Global Development, based in Washington. “His combination of passion and analytic acuity has been really important for development.”

But there are Sachs detractors. One of the most dogged is William Easterly, a former World Bank economist and author of “The White Man’s Burden,” a book that critiques aid projects.

Mr. Easterly argues that the Millennium approach would not work on a bigger scale because if expanded, “it immediately runs into the problems we’ve all been talking about: corruption, bad leadership, ethnic politics.”

He said, “Sachs is essentially trying to create an island of success in a sea of failure, and maybe he’s done that, but it doesn’t address the sea of failure.”

Mr. Easterly and others have criticized Mr. Sachs as not paying enough attention to bigger-picture issues like governance and corruption, which have stymied some of the best-intentioned and best-financed aid projects.

For example, one can easily picture what would happen in Kenya, where corruption is essentially a national pastime, if there were a free, donor-supported fertilizer program for the entire nation. The fertilizer would very likely never reach its intended target and would disappear like the national grain reserves that were plundered during a famine in 2008, or the billions of dollars of foreign aid that have ended up in the pockets of Kenyan politicians, according to numerous reports by human rights groups and financial auditors.

Mr. Sachs says he is the first to admit that he cannot do it all.

In Kenya, he says, to eradicate poverty nationwide, the country’s leaders would need to improve infrastructure and urban industries substantially.

“What we’re focusing on,” he said, “is about one-third of the problem.”

Another criticism is that Mr. Sachs is not evaluating his programs in a rigorous, scientific way. Many aid experts have suggested that the only way to really know if the Millennium Villages are worth the expense (around $110 per capita, per year) is to collect data from similar “control” villages that are receiving no help.

“No one would dream of ‘scaling up’ the use of a new pharmaceutical in the U.S. without rigorous evidence comparing people who got the medicine to people who did not,” said Michael Clemens, a research fellow at the Center for Global Development.

But Mr. Sachs says that “Millennium Villages don’t advance the way that one tests a new pill.”

Beyond that, he does not like the idea of going into a village, subjecting poor people to a battery of questions and then leaving them empty-handed, though other aid specialists have said that studying poor people without giving them anything in return is done all the time.

“It pains me to be in a village that doesn’t have bed nets” to protect against malaria-carrying mosquitoes, he said, adding that some comparison studies were under way.

It also pains him how out of touch the American public seems.

“The mood in the country right now is very anti-aid, and they don’t connect the dots very well,” he said, before launching into a discussion about the links between poverty and terrorism.

A few years ago, Mr. Sachs said, he came back from Yemen, which has recently become a haven for Al Qaeda, and spoke to American officials about how the country was “broken by hunger, water-stress, disease and poverty” and “sliding closer to the cliff.”

“I told our government all about this,” he said. “But all I got back was a blank stare.”