WASHINGTON >> Angry activists shouted “stand up, fight back” and one protester was arrested, as Betsy DeVos made her first visit to a public school today as education secretary.

Several dozen protesters, some with small children, gathered at Jefferson Middle School, a predominantly African-American school in the nation’s capital. At one point, when DeVos tried to enter the school, two protesters blocked her path, forcing her to return to her car. D.C. police said one man was detained for assaulting a police officer.

DeVos eventually made it inside the school, in a visit that was designed to help her mend fences with teachers and parents across the country following a contentious confirmation battle.

DeVos praised the school for its hard work and innovative approaches to teaching and vowed to strengthen public education. But she also had some tough words for the protesters.

“I respect peaceful protest, and I will not be deterred in executing the vital mission of the Department of Education,” DeVos said in a statement. “No school door in America will be blocked from those seeking to help our nation’s school children.”

DeVos, 59, is a billionaire Republican donor who spent more than two decades promoting charter schools and school voucher programs in her home state of Michigan and other states. She faced fierce opposition during the confirmation process from teachers unions who fear that she intends to defund traditional public schools. Two Republican senators from rural states that rely heavily on public schools opposed the nomination and Vice President Mike Pence had to cast a tie-breaking vote Tuesday.

DeVos’ visit itself was not advertised by the Education Department and was closed to the news media. Besides the arrest, police were investigating an allegation of assault on Secretary DeVos.

Randi Weingarten, president of the American Federation of Teachers, one of the groups that vigorously opposed DeVos’ nomination, condemned the incident.

“Just heard a protester blocked & almost knocked Secy BetsyDeVos down at Jefferson,” she wrote on Twitter. “We don’t condone such acts.”

D.C. Mayor Muriel Bowser also stressed on Twitter that protests should be peaceful. “We welcome Betsy DeVos & anyone who wants to learn more about our schools,” she wrote.

DeVos’ visit to the school was not announced by the Education Department.

Jennifer Ibrahim, 34, a humanitarian worker, brought her toddler son in a stroller to the protest.

“I want to support our local public schools, make sure that everybody gets fair treatment under the system and I don’t feel like that’s where we are headed with our new education person,” Ibrahim said. “Charter schools aren’t necessarily better than public schools.”

Ari Schwartz, 26, a nonprofit worker, held a poster in which a picture of a teddy bear was juxtaposed with a photo of Devos. “This is a bear. This is a threat to students,” the caption read.

During her confirmation hearings, DeVos suggested that schools should have guns on campus to protect students against grizzly bears.

Public schools are “the foundation of our society, that’s how everybody learns what’s right and wrong,” Schwartz said. “We need to keep it that way.”

Elizabeth Davis, president of the Washington Teachers Union said teachers will continue to fight for good public education and hope DeVos will listen to them.

“We want quality public schools … for all of our children in every zip code in D.C.,” Davis told The Associated Press ahead of the protest. “We do not want to continue a trend of starving, punishing and closing our public schools to make way for privatization and more charter schools and vouchers.”

But former Education Secretary Arne Duncan, who served under President Barack Obama, tweeted: “Agree or disagree w Betsy DeVos on any issue, but let’s all agree she really needs to be in public schools. Please let her in.”