The new graduation rate statistics for the city’s small schools — 73%, well above last year’s citywide average — are giving city school officials cause to smile and pronounce them a success. Others are skeptical, including some education professors, opponents of mayoral control, and the alumni association of the Erasmus Hall High School in Brooklyn.

Representing such diverse graduates as Barbra Streisand and art collector Arthur Sackler, as well as dropouts who include Moe Howard of the Three Stooges and the fugitive chess champion Bobby Fischer, the Erasmus Hall High School Alumni Association has been involved in the school’s everyday happenings for two decades. Lately, a main concern has been how Erasmus, once a single campus populated by about 5,000 students, is being broken down into separate small schools, such as the High School of Service and Learning and the Science, Technology, and Research Early College High School.

“It’s an abomination,” Alan Stein, Class of 1946 and the association’s vice president, said of the school’s being divided.

While some challenge small schools on the grounds that they allegedly block out immigrants and special education students, or that they receive extra resources, Mr. Stein and other alumni say Erasmus Hall’s students have been shortchanged. “When I went to Erasmus, we had a band, we had an orchestra, we had a choir — I can’t tell you how many different clubs,” he said. “There’s none of that now.”

The association’s treasurer, Phyllis Nathan, Class of 1963, said that, when she was at Erasmus, there were so many options that not only was she a cheerleader, she wrote for the school’s geology magazine. There is little an alumni association can do to change school policy; Mr. Stein says a board member attended an early community hearing on the first decision to split Erasmus Hall but reported back that it was a “done deal.”

Yet the Erasmus Hall alumni have refused to stand idly by. Alumni have supported activities that stretch across the schools, keeping the school’s football team afloat and buying the cheerleaders uniforms. They subsidize college scholarships, send students to Broadway shows, and help students pay for a senior trip.

In 2004, they waged a letter-writing campaign to convince the department to attach the words “Erasmus Hall” to each small high school’s name.

“Lainie Kazan called the mayor,” Ms. Nathan said, referring to the singer and actress. “Barbra Streisand called up her friends in politics.”

A letter from a surgeon from the Class of 1963, Ed Golembe, criticized the available research on small schools, citing “poor scientific quality due to the lack of paired study and control groups.” Told that the latest data show the Erasmus schools’ graduation rate at 92%, Dr. Golembe, who volunteers as a physician to the football team, said he was impressed. But he added: “I think particularly adolescents, young adults, need a sense of grounding and — where can they come together?”