Enrollment in the Pittsburgh Public Schools fell just over 5.7 percent in the past year, one of the largest decreases in a decade. Superintendent Mark Roosevelt blamed demographic trends, but critics fear it is partly attributable to unpopular changes he has made.

The district on Sept. 28 counted 26,649 students in kindergarten through 12th grade, down 1,616 from a year ago.

While some individual schools saw gains, overall enrollment fell in accelerated learning academies, K-8 schools, K-5 schools, middle schools and high schools -- every category except schools for children with disciplinary problems.

Many urban districts are experiencing enrollment declines because of the attractiveness of suburban and charter schools, among other reasons. Mr. Roosevelt yesterday blamed the Pittsburgh district's losses on "city flight," an aging population and other demographic issues.

For example, he said the demolition of public housing in Garfield may be responsible for the loss of students at Fort Pitt PreK-5, an accelerated learning academy. The school has 292 students, down 93 from a year ago.

"There's a lot happening here," Mr. Roosevelt said, adding that the district hopes to begin a project to find families that have left the district and ask them why they relocated.

The district had 39,603 students in fall 1998. It has lost students in each of the past 10 school years, including a drop of about 6.6 percent from 2001-02 to 2002-03 and a drop of about 5.7 percent from 2003-04 to 2004-05.

Pittsburgh Federation of Teachers President John Tarka said his members are working with the district to improve the district's academic reputation and reverse the enrollment decline.

"We also know the Pittsburgh Promise is an important ingredient," Mr. Tarka said, referring to the college scholarship program for city high school graduates that's intended to lure families to the city and help retain those already here.

During the past three years, Mr. Roosevelt has closed and consolidated schools, introduced new curricula and made other changes, hoping to right academics and finances. Critics displeased with Mr. Roosevelt's changes, including the closing of the Pittsburgh Schenley High School building in June, have suggested that he's driving some families from the district.

Mr. Roosevelt yesterday disputed that idea, saying enrollment numbers conform to state projections that are based on demographics.

He added that ninth-grade enrollment at Pittsburgh Frick 6-9 in Oakland and the new university-prep school in the Hill District show that the Schenley decision hasn't caused parents to pull students from the district.

Frick and the university school together have about 270 ninth-graders, most of whom would have gone to the Schenley building had it remained open. Mr. Roosevelt said enrollment at the Reizenstein building in Shadyside -- new home to Schenley's 10th, 11th and 12th graders -- is a healthy 694.

Enrollment over the past year fell by about 9.5 percent, or 334 students, at the accelerated learning academies; by about 6.3 percent, or 382 students, at K-8 schools; by about 8 percent, or 285 students, at middle schools; and by about 8.8 percent, or 739 students, at high schools. Enrollment at K-5 schools was down 15 students, about 0.2 percent, and enrollment at schools serving children with disabilities was down seven students, or about 2 percent.

Enrollment in schools serving children with discipline problems was up about 46 percent, or 146 students. Most of the increase came from the referral of additional students to the North Side alternative school that Community Education Partners operates for the district.