A snapshot from one of two Panel for Educational Policy meetings about school closures in 2011.

Boisterous protests against school closures have long been accused of lending a circus-like atmosphere to the annual meetings where the Panel for Educational Policy votes on closures. This year, though, the opposition will actually have three rings.

Three separate groups are planning protest actions during tonight’s PEP meeting, where the citywide school board is set to vote on — and presumably approve — 23 school closures and truncations. (Changes to two schools were taken off the table yesterday.)

City officials have vowed not to let the protests disrupt the panel’s proceedings, suggesting that panel members and protesters alike could be in for a long and potentially combative night. Last year, the panel approved 22 closures in two separate meetings that each lasted well past 1 a.m. In 2010, the panel’s vote on 20 school closures took place just before 4 a.m., after more than 10 hours of protests and public comment.

Tonight, the United Federation of Teachers, which has orchestrated the most substantial protests in the past, is planning to start its protest outside Brooklyn Technical High School but then constitute an alternate event, a “People’s PEP,” at P.S. 20, an elementary school with a 600-seat auditorium six blocks away that the union has rented for the evening. Union officials said teachers from the schools up for closure would be invited to give presentations about their schools at the P.S. 20 meeting.

Another group that has been active in opposing the closure proposals, the Coalition for Educational Justice, is taking a different approach: Instead of walking out from the meeting, CEJ members and those active in affiliated groups, including the Alliance for Quality Education and the Urban Youth Collaborative, are marching in protest to it. After a 5 p.m. rally, they’ll walk five blocks east on Dekalb Street to Brooklyn Tech, where they will continue to protest against the city’s proposed closures.

A press advisory for the CEJ event warns that protesters will use the “people’s mic” to amplify their voices during the panel meeting. And they won’t be alone using that strategy. A third protest set for tonight is by “Occupy the DOE,” which grew out of the Occupy Wall Street movement that popularized the human microphone tactic.

The stated goal of the Occupy protesters is to stop the panel from conducting its business by holding an alternate, “democratic” meeting in the same space. Occupy the DOE protesters derailed a special meeting of the panel last fall, and students steeped in Occupy tactics caused Schools Chancellor Dennis Walcott to cut short a town hall meeting in the Bronx last week.

A key difference is that tonight’s votes must happen — and, according to the state’s open meetings law, they must happen in public, after public input.

But Walcott said he would not let tonight’s meeting be driven off course by protesters and accused the union of masterminding the Occupy protest in addition to its own.

“There are important proposals up for discussion tonight and my hope is that we will have a respectful process where people can be heard,” Walcott said in a statement. “But if all the UFT wants to do is bus in Occupy Wall Street to disrupt public meetings — which provides absolutely no benefit to students — then we will just have to work around that.  We are prepared to move forward even if there are disruptions.”

The UFT provided some support for the Occupy movement this fall, but it is not providing transportation expressly for Occupy protesters, according to union officials. Still, they said, it is possible that some Occupy-affiliated protesters might board the 13 buses the union is running for families and teachers at schools up for closure. Most of the buses will come from schools in the Bronx, eastern Brooklyn, and Staten Island that could be closed tonight, and Harlem’s Wadleigh Secondary School for Performing and Visual Arts is expected to fill two buses even though its middle school is no longer at risk.

If the protests prove overwhelming for city officials and panel members, state law does allow the votes to be delayed. While the PEP has typically voted on closure proposals in early February, it can legally approve closure proposals up until the end of the school year as long as it has met deadlines for informing the public about the proposals and holding public hearings at each of the affected schools.

Hearings for the 23 schools up for closure tonight took place over the last few weeks. In the coming weeks, the department is poised to formally propose as many as 33 additional closures under the federally mandated school improvement strategy known as “turnaround.” If the city moves forward with those plans, which Mayor Bloomberg announced during his State of the City address last month, it would need to hold additional public hearings and the PEP would need to vote on the proposals. The city has said that would likely happen at the panel’s April meeting.