When Harlem Success Academy 2 returned for its second year at 301 W 140th St., it added grades – a typical practice for charter schools, Jenny Sadlis, director of Success Charter Network’s external communications, said via email. With a growing student body, though, the school needed more classrooms and moved into some previously used by P.S. 123, with which it shares the building. The action further strained the relationship between the schools and in the surrounding community.

Parents and advocates for P.S. 123, the Mahalia Jackson Academy, have complained that the charter is taking away space without concern for the public school students. William Hargraves, whose niece attends P.S. 123, charged that the Department of Education favors charters over regular public schools.

Harlem Success Academy, whose current enrollment is 361, serves kindergarten through second grade; it eventually plans to expand to eighth grade. P.S. 123 has an enrollment of 630 students this year in pre-kindergarten through seventh grade.

The tensions began when the charter school first moved into the building, but increased this year when P.S. 123 lost its computer room to the charter school, as well as part of its teachers’ lounge and half its library, now devoted to Harlem Success Academy office space, said Hargraves.

P.S. 123 was offered basement rooms to replace some of the space Harlem Success Academy has commandeered, but “there’s no way a kid can learn in that environment,” Hargraves said, describing the basement as “no more than a storage area.” The school squeezed in classes elsewhere in the building.

Space is allocated in all schools across the city based on “a footprint” the Department of Education determines, said spokesperson William Havemann. While the footprint allocates the number of each type of classroom a school should have, based on its enrollment, “it does not determine which particular rooms in a building go to each school,” he said. The school officials decide that themselves.

“A lot of work went into the agreement between P.S. 123 and Harlem Success, and both schools participated in discussions,” said Havemann in a follow-up email.

But Hargraves still feels that the Harlem Success Academy “has the choice of the best rooms.”

The charter school, however, maintains that it has divided space fairly. “We treat all of our roommates with the utmost respect,” Sadlis said.

But Dianne Johnson, president of Community Education Council 5, said the Academy sometimes demonstrates a “disrespectful” attitude toward its public school neighbors. “If we have to be in the same building, then we all need to learn how to get along,” she said.

Parents, teachers and students have held rallies opposing the charter school since last year. At the most recent, held last month before the Academy’s annual parent appreciation event at the Roseland Ballroom, the chants ranged from “The people united will never be defeated” to “Eva Moskowitz must go” – a reference to Harlem Success’s founder. They plan to continue the rallies, Hargraves said at the time, but have not held once since then.

For Hargraves, the issue goes beyond the competition with the Harlem Success Academy. Mayor Michael Bloomberg and his administration have abandoned public schools and favor charter schools, charged Hargraves, who at the rally led chants of “Bloomberg lies while public schools die.”

Mabel Moody Washington, however, has two grandchildren in the Harlem Success Academy, primarily because it provided a better education than regular public schools, she said; she is unapologetic about that choice.

She sees the Harlem Success Academy as helping disadvantaged communities catch up to the more privileged. “For centuries, our children have lagged behind. Now they’re not,” she said. “You leave there with the academic skills you need to succeed.”

The charter was ranked number 32 out of 3,500 schools in the city, according to its website. One hundred percent of its third graders passed last year’s math exam. At all four Harlem Success schools, 95 percent of third graders passed the English Language Arts exam.

P.S. 123 is rated a successful school too. It received an A from the Department of Education last year, and a B each of the prior two years. But although 77 percent of its third graders passed the math exam, just 39 percent passed the English Language Arts exam.

While Johnson said she doesn’t oppose charter schools and thinks that parents deserve educational choices, she feels that regular public schools deserve more respect. “It’s like you’re picking, your children are better than my children,” she said. “It’s starting to cause a whole lot of controversy from neighbor to neighbor.”

Johnson said she has contacted Moscowitz about forming a committee, with representatives from both schools, to work together, but Moscowitz has not yet replied.

“We are not aware of any such request,” Sedlis said.

But Johnson said she planned to try again. “The only thing I can do is keep reaching out,” she said. “It’s up to her to respond.”