NEW YORK - The lecture hall had filled quickly. Several students wore keffiyehs, the traditional Palestinian headscarves, while another sat draped in the Israeli flag.

It was time for a ritual that has become increasingly commonplace on many American college campuses: A student government body, in this case at the University of California, Davis, would take up Israeli policy toward the Palestinians, and decide whether to demand their school divest from companies that work with the Jewish state.

In the United States, Israel's closest ally, the decade-old boycott-divestment-sanctions movement, or BDS, is making its strongest inroads by far on college campuses. No U.S. school has sold off stock and none is expected to do so anytime soon. Still, the current academic year is seeing an increasing number of divestment drives on campus. Since January alone, student governments at four universities have taken divestment votes.

While the campaigns unfold around resolutions largely proposed by chapters of Students for Justice in Palestine, outside groups have become increasingly involved - from American Muslims for Palestine and the Quakers' American Friends Service Committee, on one side, to the American Israel Public Affairs Committee, or AIPAC, on the other. At some campuses, candidates for student government are being asked their views on the Israeli-Palestinian conflict. The heated rhetoric has led to claims of anti-Semitism and of infringement on free speech.

"I don't think anyone is surprised when they hear a BDS movement is coming," said Ira Stup, a 2009 Columbia University graduate and former director of J Street U, the college arm of the liberal pro-Israel lobby J Street, which opposes BDS. "It's becoming a regular occurrence."

"It's creating a debate. It's creating a significant amount of conversation in the entire community and it's set on the terms the activists want it to be set on," said Rahim Kurwa, a doctoral candidate and member of Students for Justice in Palestine at the University of California, Los Angeles.

The boycott-divestment-sanctions movement grew from a 2005 international call from Palestinian groups as an alternative to armed struggle over control of the West Bank, Gaza and east Jerusalem, which Israel captured in 1967 and Palestinians seek for an independent state.

BDS advocates say the movement, based on the campaign against South African apartheid decades ago, is aimed at Israeli policy, not Jews, in response to two decades of failed peace talks and expanded Israeli settlement of the West Bank and east Jerusalem.

But supporters of Israel say that boycotting the country is no way to make peace, especially since many BDS supporters do not differentiate between protesting Jewish settlements on occupied lands or Israel as a whole.

In the U.S., activists have pressed for boycotts of Israeli products and cultural events, and divestment by churches and others. None of these efforts has gained as much momentum as the campus divestment movement.

College activists organize lectures and workshops on Israeli policy and Palestinian history, while staging protests that include mock Israeli military checkpoints, or a mock West Bank separation barrier that activists call an "Israel apartheid wall." Pro-Israel groups counter with their own demonstrations and events. When student governments prepare to vote, the hearings can last for days, drawing campus-wide attention.

Only a few dozen student governments have cast ballots on divestment proposals since 2012. Of those votes, about a dozen have won passage. University administrators and boards - not student governments - oversee investments, and trustees have widely rejected divestment. The University of California Board of Regents said they would only divest from companies working in a country that the U.S. government said was committing genocide.

Still, the campaigns have succeeded in challenging students to re-consider their views of Palestinians.

Nowhere is the impact more evident than the University of California system. Student governments at five of the 10 UC campuses have voted for divestment. Two more, Santa Cruz and Davis, did the same, but the votes were thrown out over procedural issues. Since December, divestment also won the backing of the labor union representing thousands of teaching assistants and other workers for the entire UC system, UAW2865, and the University of California Students Association, which represents student government bodies statewide.

"The movement is getting more and more organized," said Roz Rothstein, chief executive and co-founder of the California-based group Stand With Us, which helps train students to defend the Jewish state. "The strategy is being shared across campuses."

National groups on both sides have been building up networks to support student activists.

Along with training and advocacy groups, divestment advocates now have a new source of legal support. In 2013, the Palestine Solidarity Legal Support Fund launched with the help of the Center for Constitutional Rights and others. Fund director Dima Khalidi said her group received 230 requests for help in 2014, and about 70 percent came from college students and faculty who said they were being harassed or unfairly punished by school administrators.

Meanwhile, every major American Jewish group has in some way put resources into countering divestment and the uptick in anti-Israel activity. In 2010, after pleas from Jewish leaders, Education Secretary Arne Duncan extended protection to Jewish students under the Title VI civil rights law. So far, no school has been found in violation.

Kurwa of Students for Justice in Palestine contends divestment drives will continue spreading to new campuses "the longer the status quo drags on without any realistic hope for some kind of solution." Rothstein, of the pro-Israel Stand With Us, said her group is expanding "as fast as we can."