By Wilfred Chan, CNN

Updated 4:27 AM ET, Tue June 23, 2015

The decision means the Ivy League school -- with boasts a roughly $9 billion endowment -- will sell its roughly 220,000 shares in G4S, the world's largest private security firm, as well its shares in the Corrections Corporation of America (CCA), the largest private prison company in the United states.

The campaign began in early 2014 when a small group of Columbia students discovered tuition money was being invested in the two firms, which run prisons and detention centers and militarized borders.

The group, called Columbia Prison Divest, launched protests and meetings with administrators where they argued it was wrong for the elite school to invest in a "racist, violent system."

"The private prison model is hinged on maximizing incarceration to generate profit -- they're incentivized by convicting, sentencing, and keeping people in prison for longer and longer times," Dunni Oduyemi, a 20-year-old organizer, told CNN.

"We don't think about how the privileges and resources students get access to are premised upon violence done to people by virtue of their race, class, or citizenship status."

In an emailed statement, a Columbia spokesperson said the university's trustees had decided to divest from private prison companies and would refrain from investing in such companies again.

"This action occurs within the larger, ongoing discussion of the issue of mass incarceration that concerns citizens from across the ideological spectrum," the statement said. "The decision follows ... thoughtful analysis and deliberation by our faculty, students, and alumni."

The spokesperson would not confirm how much Columbia had invested in the two companies.

In 2007, Farallon, a company managing part of Yale University's endowment, also divested from CCA after a student campaign, though it did not rule out future investment in prison stock.

History of controversy

Oduyemi said activists targeted CCA for its "horrific" human rights record. A 2014 ACLU investigation found abuse and neglect in CCA-run prisons where guards used "extreme isolation arbitrarily and abusively," exposed prisoners to contaminated water, and delayed medical care of inmates, causing "needless suffering."

Student activists also targeted G4S, a British firm, which has supplied a prison in the West Bank and checkpoints in Palestinian territories. Until last year, the firm also had a contract to provide services at U.S. detention facilities in Guantanamo Bay, according to the Financial Times. The firm still maintains patrols along the U.S.-Mexico border.

South African prisoners have sued the company over claims they were tortured, according to the Guardian.

Nigel Fairbrass, a G4S spokesman, defended the company's conduct.

"We actively followed up with the South African government and have been presented with no evidence to substantiate the allegations," Fairbrass wrote in an email to CNN. "The prison was also returned to our operational control last year."

He added that a 17-month investigation by the OECD's United Kingdom contact point had not found any human rights violations in G4S's operations in Israel -- and said the company would also not renew its contracts in Israel once contracts there expired over the next two years.

CCA did not immediately respond to CNN's calls and emailed requests for comment. CCA's website includes a statement committing to "respecting human rights."

Will divestment have an impact?

Oduyemi said G4S had been responsive to past divestment campaigns, and "that has been the only effective way of getting them to change the contracts they write."

But Fairbrass said Columbia's holdings of G4S stock, around 220,000 shares, comprised just 0.015% of G4S' market cap, valued today at $4.35 billion.

Similarly, CCA has a market cap of $4.01 billion. Both firms are highly profitable and continue to grow.

Alex Friedmann, the managing editor of Prison Legal News, a project of the nonprofit Human Rights Defense Center, predicted the divestment would have little to no effect on companies' stock price or operations.

"I don't see divestment campaigns making a big dent," he told CNN. "They serve more as public education on private prisons, organizing tools, or as social commentary on what people believe is acceptable to be investing in."

"As long as prison companies have the bed space the government needs and wants, they will most likely stay in business."

Although Columbia is the first U.S. university to announce divestment from private prisons, similar campaigns are ongoing at other institutions, including Cornell, Brown, U.C. Berkeley, and UCLA.

"It seems to be a moment where people are making the connection between all the kinds of uprisings we're seeing right now — #BlackLivesMatter, mass incarceration, and university movements," said Oduyemi. "We all recognize how much work has to be done in the future."