WASHINGTON — Randi Weingarten, president of the American Federation of Teachers, the second-largest teachers’ labor union in the nation, said illegal immigration makes America’s public school system “stronger” by bringing more diversity. She attributed overcrowding to charter schools, austerity, and privatization.

Some school districts are grappling with classroom overcrowding and English proficiency issues among their student populations. Undocumented immigrants are able to enroll their children in public schools regardless of their immigration status or the status of the children.

Weingarten appeared at a rally outside of the White House on Friday where protestors called for the closure of detention centers for undocumented immigrants caught attempting to cross into the U.S. without authorization. The protestors also called for the Trump administration not to separate children from parents who are apprehended at the border for illegal entry.

“Classrooms, not cages,” speakers shouted at the protest, which consisted of many AFT TEACH conference attendees.

Weingarten was asked how the public school system would be able to handle the added influx of undocumented migrants if detention centers were to close. She attributed classroom overcrowding to school choice voucher programs.

“Actually, what hurts the public school system is when charter schools take money out of public schools and that’s what creates overcrowding. What hurts the public school system is when state after state after state doesn’t pay its fair share and has actually spent less money on public schools — 21 states that is — than it did 10 years ago,” responded Weingarten, whose union has 1.7 million members. “We have, as a country, an obligation to help all of our children and ultimately when we do, we are better for it.”

In 2015, it was estimated that 540,000 students went to schools that were at capacity in New York City. A study from the group Make the Road New York found that overcrowding is worse at schools in areas with large immigrant populations.

“Using census figures and data from the city’s own capital plan for school construction, the group’s research coordinator, Daniel Altschuler, said overcrowding is ‘particularly pernicious in immigrant communities,'” read a report on the study. “As the immigrant population in a particular district increases, so too does the overcrowding problem.”

During the surge of unaccompanied minors at the border in 2015, school districts were struggling to accommodate the added influx of students.

“We need more space, we need more teachers, we need more social workers, we need more staff,” Lamont Johnson, the school board president in Hempstead Union Free School District in Long Island, New York, said at the time. “[The children] need social workers, counselors, different people to help them transition to a new environment.”

Responding to concerns about the effects of classroom overcrowding and English proficiency issues on the learning experience at public schools, Weingarten said, “I think there are a lot of things that actually hurt public schooling and it starts with austerity and privatization but at the end of the day, every community is better off when it has new influx of people who bring their passion, their souls, their abilities and things like that. We will never turn anyone away and that is who we are as a strength of a nation. Our diversity is part of what makes us stronger.”