Much to their dismay, Horace Mann Middle School teachers discovered last week that when classes resume in the fall they will be sharing their campus on 23rd Street and Valencia with a five-year-old charter high school.

The district “screwed up,” said Mark Sanchez, Horace Mann’s principal, referring to the way in which it made the decision to give Metropolitan Arts and Technology High School a one-year lease. “The entire staff is against it.”

Sanchez said he favored Metro’s project-based approach to education, but would not go against his staff’s plans to protest. He said there was room for both schools to co-exist. Horace Mann has about 330 students and Metro about 200.

On Saturday, the two schools eyed one another from their respective booths at a community fundraiser for a proposed Mission District farmers market. They were the only two public schools at the fundraiser.

Horace Mann's table at Saturday's community fundraiser.

One teacher from Horace Mann said they discovered Metro’s move-in plans by chance last week when a parent from Metro told a teacher he knew at Horace Mann. Teachers and some parents had already made their opposition clear in April when the district first proposed the idea. “It’s not right,” the teacher said about the process in which the district simply makes a decision without consulting them.

Mark Sanchez, principal of Horace Mann Middle School.

Abby Benedetto, a Metro teacher, tried to make the best of an awkward situation. “For me it’s just sad because their protest has nothing to do with our school, just the process,” she said, looking across 22nd Street to Horace Mann’s table and banner. “ I know Horace Mann is feeling like they are getting the short end with the school district, but we’ve moved four times in five years.”

Benedetto said Metro would gladly take any graduating eighth-graders from Horace Mann. “We represent a path for some of those marginalized kids,” she said. Some 91 percent of Metro’s graduating seniors were eligible to attend a California state university, and 95 percent plan to enroll in either a two- or four-year college in the fall.

Metro, run by the nonprofit Envision Schools, opened in 2005 on Treat Avenue in the Mission District, moved to Fillmore and Jackson in 2007, and to Phillip and Sala Burton Academic High School in the Bayview District in 2008.

Metro’s former principal Glenn Dennis, who was also at Saturday’s fundraiser, said the school had always planned to return to the Mission.

Dennis, who will be an assistant principal in San Rafael next year, said that 50 percent of Metro’s students come from the Mission-Bernal corridor, and 70 percent are eligible for free or reduced lunch.

“We’re project-based and about getting students ready for the 21st century,” he said.

Metro needed to move, he wrote later in an e-mail message, because at Burton “only 40 percent of the classrooms have access to natural light. The building is old and not painted. The classrooms leak. You get the picture.”

Metro saw Horace Mann as its best option because of its Mission District location and its dwindling enrollment. Proposition 39, approved by voters in November 2000, requires the district to provide facilities for charter schools.

Horace Mann, built to hold some 600 students, now has about 330. It is on a state list of 10 struggling San Francisco schools and is planning major changes, including the introduction of project-based learning and a Spanish immersion program.

Metro’s students would take over the eight classrooms in what is now known now as the sixth-grade annex, a separate building. They would also use five classrooms in the main building, Sanchez said.

Metro is one of four charter high schools run by Envision, a nonprofit charter school operator founded in 2002 and based in San Francisco. It also operates City Arts and Technology High School in the Excelsior, Envision Academy in Oakland and Impact Academy in Hayward.