Education secretary nominee Betsy DeVos voiced strong support for public school alternatives at her confirmation hearing Tuesday, telling senators that "parents no longer believe that a one-size-fits-all model of learning fits the needs of every child."

DeVos told the Senate Health, Education and Pensions Committe that she would be "a strong advocate for great public schools" if confirmed, but added that "if a school is troubled, or unsafe, or not a good fit for a child ... we should support a parent's right to enroll their child in a high-quality alternative."

DeVos, 59, also said she will seek to address rising higher education costs and massive student debt, but also advance trade and vocational schools as well as community colleges because "craftsmanship is not a fallback — but a noble pursuit."

President-elect Donald Trump's nomination of DeVos to lead the Department of Education was harshly criticized by teacher's unions, who have claimed that DeVos wants to undermine the public education system, which provides instruction to more than 90 percent of the country's students.

In his opening statement, committee chairman Lamar Alexander, R-Tenn., himself a former secretary of education, said DeVos is "on our children's side."

"I believe she is in the mainstream of public opinion, and her critics are not," said Alexander. That praise was echoed by Sen. Tim Scott, R-S.C., who introduced DeVos to the committee by calling her "a champion of education, and specifically a champion of education for poor kids."

Former Connecticut Sen. Joe Lieberman also appeared before his onetime colleagues to introduce DeVos.

"We just can't accept the status quo in education anymore," Lieberman said. "We need a change agent and an education reformer to be education secretary ... and that is exactly the kind of education secretary I believe Betsy DeVos can and will be."

Sen. Patty Murray, D-Wash., the committee's ranking member, expressed concern that lawmakers had not received an ethics review for the nominee.

"I am extremely disappointed that we are moving forward with this hearing without receiving the proper paperwork from the Office of Goverment Ethics," Murray said.

Murray also told DeVos that federal policy should be focused on strengthening public schools, "and certainly not toward diverting taxpayer dollars to fund vouchers that don't work for unaccountable private schools." She asked DeVos point-blank to pledge that she would not seek to privatize public schools or take money away from them.

DeVos, whose husband is the heir to the Amway marketing fortune, has for decades used the family’s influence and wealth in her home state of Michigan to advocate for charter schools and promote conservative religious values. Critics of DeVos have expressed concerns about her financial contributions and possible conflicts of interest.

The nominee attempted to assuage those concerns during the question-and answer period, pledging that she "will not be conflicted. Period." DeVos also said that she will take a government salary of $1 if confirmed.

Asked outright by Sen. Bernie Sanders, I-Vt., if she got the job because of her family's political contributions, DeVos said: "As a matter of fact I do think that there would be that possibility. I have worked very hard on behalf of parents and children for the last almost 30 years."

On tuition-free public colleges and universities, DeVos said: "I think we also have to consider the fact that there is nothing in life that is truly free. Somebody is going to pay for it."

She skirted Sanders' question on whether she would support making child care free or much more affordable for low-income families as is the case in many countries around the world, saying only that she feels strongly about "parents having an opportunities for child care for their children."

"But it's not a question of opportunity," Sanders fired back, raising his voice. "It's a question of being able to afford it!"

As the hearing dragged on into its fourth hour, Democratic senators made repeated requests with Chairman Alexander to allow them to pose another round of questions to DeVos, but he refused, citing procedures at previous hearings.

DeVos is expected to get enough votes in the committee and before the full Senate to be confirmed, considering she needs only a simple majority, with Republicans having 52 senators and Democrats having 48.

In a letter addressed to the committee, 38 prominent education groups and teachers' organizations expressed concern that DeVos' track record bodes ill for public education.

"Over the course of her career as a major campaign contributor, soft-money donor and lobbyist, DeVos has used her considerable wealth to influence legislation and the outcomes of elections to advance policies that have undermined public education and proved harmful to many of our most vulnerable students," the letter said.

LGBT groups also have protested Trump's choice of DeVos, saying she has funded conservative religious groups that promote what they consider to be traditional family values, including one organization that supports conversion therapy -- counseling of gay, lesbian, bisexual or transgender people with the aim of changing their sexual orientation.

DeVos repeatedly disavowed any support for conversion therapy Tuesday, saying in her opening statement that "every child in America deserves to be in a safe environment that is free from discrimination."

Under questioning from Sen. Al Franken, D-Minn., DeVos said that "I have never believed in" conversion therapy and "I believe in the innate value of every single human being."  Alexander later read into the record a letter of support from the Log Cabin Republicans, a Republican organization pushing for LGBT rights.

DeVos supporters, meanwhile, applauded her nomination. Eva Moskowitz, CEO of Success Academy Charter Schools, said that American public education "is in deep crisis," with 35 countries outranking American schools in math and 20 in reading.

"I believe Betsy DeVos has the talent, commitment and leadership capacity to revitalize our public schools and deliver the promise of opportunity that excellent education provides, and I support her nomination as U.S. secretary of education," Moskowitz said in a statement.

DeVos has also garnered strong backing from two dozen state governors, as well as another former education secretary, William Bennett.

It’s time we take a major turn in American education,” Bennett told Fox News Channel’s “Happening Now” on Tuesday. “Betsy DeVos represents a change. She is experienced in the field with children from all over the country. … She understands what the problems with education are.”

The Associated Press contributed to this report.