A number of returning D.C. secondary school students have found mistakes in their class schedules, a situation that school officials attributed yesterday to the conversion to a new computer system.

Some students, for example, were assigned courses they already had taken or were not placed in courses they need to graduate. But officials said the problems are not as serious as last year, when hundreds of students at Eastern Senior High School in Northeast Washington were turned away on opening day because their schedules had not been completed. Eastern's principal and two other officials were fired immediately over that incident.

About 5 percent of the student schedules at the secondary level were affected by this year's glitches, said the school system's chief accountability officer, Meria J. Carstarphen.

Maria Tukeva, principal of Bell Multicultural Senior High School in Northwest Washington and assistant superintendent for senior high schools, said all the scheduling problems should be cleared up by today.

"Scheduling is real complicated at the high school level. It's the most complex jigsaw puzzle you'll encounter," Tukeva said, adding that the majority of scheduling problems involved student transfers.

Last year's class schedules at Eastern were not completed on time because administrators had trouble entering data into a computer. This year, administrators at Eastern and other high schools used a new computer system but again encountered data-entry problems.

"If you're someone who learned how to do schedules on the old system, it's a learning curve," Tukeva said. "Your speed in doing it might be affected."

At Woodson Senior High in Northeast, "some students had schedules that didn't include all the courses they wanted to take," Principal Aona Jefferson said yesterday. "Students that failed a class had to make sure they had the right class."

Nathan Saunders, vice president of the Washington Teachers' Union, said union leaders have been helping officials at a few schools try to work out the kinks.

School officials are "aggressively tackling the problem," Saunders said. "That's a difference from the past."

In correcting the problems, Carstarphen said, "We made people go back and check it not once, but twice and three times."

The new computer system, called D.C. STARS, is designed to handle a variety of data, including records on attendance and grades, which previously were compiled by hand. The system ultimately will be used to calculate graduation and dropout rates based on following a ninth-grade class over four years and determining how many of the students stayed and how many left, a method that experts say is best. Currently, the school system determines the rates based on the number of students who stay and leave during a one-year period.

Mark Roy, a community member of the school restructuring team at Eastern, said students and administrators at the school were frustrated by this year's scheduling problems.

"STARS was billed as a Lexus," Roy said. "You look at it -- this ain't nothing but a Hyundai."

Despite the glitches, school officials said they prefer the new system.

"It's easy to manipulate and it's Web-based," Jefferson said, adding that the problems can be attributed more to people's failure to enter information correctly rather than to a defect in the computer program.

"I really like STARS," Jefferson said. "We just need more practice on it."