The city is preparing to appoint a new principal to lead long-struggling Boys and Girls High School, according to multiple sources, and is leaning towards an assistant principal from the Bronx.

If the education department chooses Grecian Harrison, an assistant principal at Alfred E. Smith High School, it will have snubbed the choice of staffers and alumni at Boys and Girls. They have coalesced around Allison Farrington, the founding principal of Research and Service High School, a small school for struggling students housed inside Boys and Girls’ historic Bedford-Stuyvesant, Brooklyn campus. Sources said an announcement could come as soon as Monday.

The city has scrambled to find a new leader for Boys and Girls after Principal Michael Wiltshire decided last month to leave the school after less than two years. His abrupt departure has shaken the school at the center of the city’s high-profile turnaround program for troubled schools, leaving its future uncertain even as it remains under intense pressure to improve.

Once dubbed the “Pride and Joy of Bed-Stuy,” Boys and Girls has shrunk in size and stature in recent years. Its enrollment plunged from 2,300 students in 2010 to 340 today, and its graduation rate trails the city average by 20 points.

Wiltshire slashed the school’s suspension rate and helped lift its graduation rate 8 points, to 50 percent. But as the school braces for yet another new leader, it risks shattering those fragile gains.

Deputy Chancellor Dorita Gibson is said to favor Harrison to take over Boys and Girls, according to sources. (Harrison did not immediately respond to an email, and was not at Smith on Friday.) However, the education department may not have the final say: The city signed an agreement in 2014 that gave the teachers and principals unions a role in choosing any new leader for the school.

Last month, Boys and Girls’ teachers-union representative — along with members of the school’s alumni group, parent-teacher association, and school-leadership team — signed a letter to Fariña backing Farrington, along with two other potential candidates. On Friday, as word spread through the school that officials favored Harrison, the alumni group emailed Fariña to declare Farrington their chosen candidate.

Farrington referred questions to the education department, but multiple sources said she had interviewed for the position and was scheduled to meet with Fariña last week before the meeting was unexpectedly cancelled.

Boys and Girls staffers and alumni said she is extremely popular among those who know her. To assist Research and Service students who are impoverished or homeless, she created a food pantry in the building and installed a washer and dryer, said Sam Penceal, a leader of Boys and Girls’ alumni group. She has also lured students to school on Friday by cooking them breakfast, and offers them after-school and Saturday tutoring.

“This is the sort of thing that ought to be a model of what needs to happen in” Boys and Girls, Penceal said. A person who works at Boys and Girls said that community is “1000 percent backing her.”

The letter writers asked Fariña for more input in the principal-hiring process. “We deserve the right to select a leader from within our campus village who will hit the ground running in the right direction on Day 1,” they wrote.

People at Boys and Girls said they had not met Harrison, despite their calls for a role in the search. On Friday, as Harrison’s name circulated as the department’s top pick, several people connected to the school complained about being shut out of the decision-making process.

“They talk about community engagement,” one Boys and Girls staffer said, “but when we’re engaged, they don’t listen to us.”

Education department spokeswoman Devora Kaye did not answer questions on Friday about the principal search, but said a decision was on the way.

“We look forward to building on the progress of Boys and Girls with a new principal, whom we expect to announce soon,” she said in a statement.