Education Secretary Arne Duncan speaks during a town hall meeting with President Barack Obama, Monday, Sept. 14, 2015, at North High School in Des Moines, Iowa. (Charlie Neibergall/AP)

The U.S. Department of Education announced Monday it would give $157 million to create and expand charter schools throughout the nation, despite criticisms by its inspector general in the past that the agency has done a poor job of overseeing federal dollars sent to charter schools.

Education Secretary Arne Duncan made a passing reference to oversight problems during a media call with reporters. “Some have had to fold, some are struggling to find their way,” he said, referring to poor-performing charter schools. “We know we have to strengthen oversight… The good news is that the sector has proven it can improve.”

With the addition of Monday’s grants, the department has awarded more than $3 billion to charter schools since fiscal 1995. Federal dollars find their way to charter schools through two routes. In most cases, the federal government awards money to a state, and the state hands out grants to charter schools. In some instances, the federal government directly awards money to a public charter school.

But the federal government has not tracked how its dollars have been used by charter schools, nor has it studied their academic performance.

Asked how taxpayers can be assured that federal dollars will be spent properly, Duncan said it was largely up to states and the public agencies that approve charter schools.

“It’s so important that from the academic side and the fiscal side that [charter school] authorizers and states hold charters accountable,” Duncan said. “At the federal level, we don’t have a whole lot of leverage. But we can really challenge states.”

The department sent a “Dear Colleague” letter to states, emphasizing the importance of financial accountability for charter schools receiving federal dollars. Duncan also said that his agency plans for the first time to publicly report some data, including the names of some schools that have received federal grants and their performance statistics.

The agency’s inspector general issued a scathing report in 2012 that found deficiencies in how the department handled federal grants to charter schools between 2008 and 2011.

The inspector general discovered dozens of charter schools received federal dollars but never opened their doors to students. The schools received millions in federal funds, but there was no record of what happened to the equipment, supplies or anything else purchased with the federal dollars for schools that never opened, the audit said.

Public charter schools are funded by tax dollars but managed privately and often are not unionized. Duncan has been a strong advocate for charter schools.

“We need more great public schools of all kinds,” he said Monday. “Too often, charter school successes are isolated and don’t have an impact beyond the walls of their own buildings...We’re helping [charter] schools to scale.”

For Scott Given, the founder of the UP Education Network, which operates five charter schools in Massachusetts, the $2.2 million grant means his chain can grow to 20 schools by 2020. Unlike most other charters, UP Education takes over existing public schools that have been chronically underperforming, accepting all students.

Up Education Network was among 12 charter organizations that won grants, including some well-known names such as Success Academy, the largest operator of charters in New York City, and the Noble Network of Chicago.

Seven states and Washington, D.C. won grants, including Ohio, which got the largest single award of $32.5 million. Ohio has also been at the center of several recent charter school scandals, from the Ohio state auditor finding some charters had inflated enrollment figures to evidence that some state officials inflated evaluations of charters.

Asked why the state with multiple charter school problems received the biggest federal grant, Nadya Dabby, an assistant deputy secretary at U.S. Department of Education, said she believed Ohio has improved its oversight of charter schools.

“Ohio has a pretty good mechanism in place to improve overall quality and oversight,” said Dabby, although she could not provide details. “We believe Ohio has put practices in place, although there ‘s always room for them to grow.”

With the addition of Monday’s grants, the department has awarded more than $3 billion to charter schools since fiscal 1995. In its budget request for 2016, the Obama administration is seeking $375 million for the program — a 48 percent increase over current funding levels.