Alan Ettman, an English teacher at DeWitt Clinton, one of the Bronx’s last large high schools, has been down this path before.

He taught at Walton High School, a large school just a mile south of Clinton, before a couple of small schools were “co-located” into the same building around the turn of the century. Renovations were soon done at the building for the new schools, while Walton’s facilities deteriorated and its spirit sank. At one point, Ettman literally found himself locked out of the faculty bathroom.

“I had every intention of finishing my career there,” Ettman says.

A few years later, the Department of Education decided to close Walton completely.

“It was extremely demoralizing and depressing to everyone,” Ettman says.

Ettman moved on to Clinton, where he is now the school’s chapter leader for the United Federation of Teachers, and hoping against hope that he won’t be locked out of another faculty bathroom in a few years.

Ettman and hundreds of other Clinton supporters came out to a public hearing on Feb. 21 to adamantly oppose the DOE’s plan to co-locate two new small schools at Clinton starting next fall. The co-locations are just the beginning of the end for Clinton, say Ettman and others.

“First they’re going to shrink it,” said Marvin Shelton, the president of the local community education council for District 10, a volunteer body that oversees school issues in the area. “Then they’re going to kill it.”

Despite rampant and loud opposition to the plan from Shelton, the entire school community and every local elected official in the area, Ettman says, “I’m not terribly optimistic” about the school’s chances of defeating the proposal, which will be voted on by the city’s Panel for Education Policy in Brooklyn on March 11. He said the whole school community is experiencing a little bit of a “malaise” about the situation.

The panel is controlled by the mayor, who has control of the city’s public school system, and is generally seen as a rubber stamp on DOE’s proposals.

Still, there is cause for some hope. A group of four panel members, all of them appointed by borough presidents, including the Bronx representative, have introduced a resolution to place a moratorium on co-locations and school closures. That resolution will be voted on during the March 11 meeting as well.

Many of the Democratic front-runners for mayor have also said they support a moratorium.

The DOE says Clinton would be able to better serve its students if its enrollment is lower. By phasing out admission to three of the school’s six programs — animal professions, future teachers and public and community service tracks — starting next fall, the DOE says it will reduce enrollment from about 3,750 students to around 2,250.

At the hearing, DOE officials said it made the decision to lower enrollment based on Clinton’s recent struggles, including a four-year graduation of 50 percent in 2012 (well below the citywide average of 65 percent), its recent “F” grade for student progress on its latest DOE report card and its ranking among the state’s 5 percent of lowest performing schools.

Ettman and other skeptics of the DOE’s plan say shrinking the school will only further erode the school’s ability to serve its diverse population of students, which range from top-flight honors students to struggling special education students and English Language Learners.

The school is already at a disadvantage in terms of dollars per student, said Ettman and others at the hearing. Ettman said the per-student spending rate is $15,684, much lower than the citywide average of $18,419.

“It is considerably more expensive to have multiple schools with multiple principals operate a building that serves the same number of kids as the large school, but does not offer a full range of classes and options for all of the students in that building,” Ettman said at the hearing. “It defies logic to even suggest it.”

Principal Geraldine Ambrosio, who is retiring this summer, urged the DOE to reconsider the co-locations, saying initiatives were in place to help improve the school and dealing with two new schools in the building would only make the new principal’s job harder.

Despite his waning optimism, Ettman says he’ll be at the March 11 meeting, fighting until the end.

Ed. Note: The public can continue to submit comments about the proposal to co-locate two small schools at Clinton until March 11, by D10Proposals@schools.nyc.gov or by phone, (212)-374-5159. The Panel for Education will meet on Monday, March 11, at 6 p.m. at Brooklyn Technical High School 29 Fort Greene Pl. to vote on the proposal.