Crystal Bailey’s son came home from school recently with a dirty uniform. Before she could fuss at him, he explained it was muck from science class.

“He’s like, ‘Guess what I learned?’ How could I be mad at that?” Bailey said.

She and dozens of other parents gathered at a public hearing Thursday night to protest plans to merge and rezone their school, P.S. 241 STEM Institute of Manhattan in Harlem.

For parents, elected officials and advocates, the plan in Harlem has grown to symbolize larger issues: school segregation and the impact of charter schools.

“This is an equity issue,” said Emmaia Gelman, a member of the group New York City Public School Parents for Equity and Desegregation.

The Department of Education has proposed to merge P.S. 241 with P.S. 76 A. Philip Randolph, and to redraw the school lines around P.S. 241. Under the plan, families currently zoned for P.S. 241 would be distributed among other local schools: P.S. 76, P.S. 180, P.S. 185/P.S. 208.

“Why do you want to unravel this institution, rather than strengthen it?” Maria Garcia, who has two children at P.S. 241, asked at Thursday’s hearing.

The proposal comes on the heels of another contentious rezoning in District 3, which spans from the Upper West Side to 122nd Street in Harlem. Both plans have highlighted stark differences among the area’s schools.

For more than a year, parents railed against plans to redraw school boundaries on the Upper West Side, where students are packed into high-performing schools. In Harlem, a rezoning plan was presented just weeks before a final vote was expected — and only after the Department of Education proposed to merge a school that has struggled with enrollment and performance on state tests.

Enrollment at P.S. 241 has hovered around 100 students in recent years, despite a federal magnet grant designed to attract families — and integrate the school — by offering a curriculum in science, technology, engineering and math. The school has seen a small uptick in enrollment recently, but parents say it has been squeezed by two charter schools that share its building.

“Why do we have to go?” asked Tasha Clarke, who has two sons at P.S. 241.

The merger and rezoning rely on two separate processes. The citywide Panel for Educational Policy is scheduled to vote on the merger in January.

The District 3 Community Education Council must ultimately vote on the rezoning. Though a vote is scheduled for Dec. 14, council members have begun to voice reservations about the plan.

“Anybody who thinks that this council has decided to vote to approve this is sorely mistaken,” council President Joe Fiordaliso said at the hearing.

Council members shared data they compiled that shows declining enrollment in the area’s schools and growing charter enrollment.

“We’re in crisis,” said council member Daniel Katz.

This isn’t the first time P.S. 241 has fought to keep its doors open. The DOE tried in 2009 to close the school and replace it with charters.

The New York Civil Liberties Union and teachers union sued, arguing that by closing a zoned school, the department was essentially redrawing attendance boundaries. That falls under the purview of Community Education Councils, which vote on all zoning decisions.

Soon after the suit was filed, the DOE dropped its plans to shutter P.S. 241. But CEC member Noah Gotbaum thinks the same issues apply to the proposed merger — and therefore the council could play a crucial role in determining the school’s fate.

“I think we on the CEC need to look at the merger very, very carefully and essentially make a decision on it,” he told Chalkbeat, “and not say that we don’t have the power or the right.”