After two all-night sessions, technology specialists at the District's school system headquarters finished assembling Eastern Senior High School's class schedules yesterday, making it possible for regular classes to start on Tuesday.

By midday, workers had successfully programmed classes for 849 of 868 students at Eastern. The remaining scheduling conflicts will be resolved manually. The school system anticipates a final enrollment of 900 to 1,000 students.

The schedules were printed and driven to Eastern about noon and were distributed starting at 1:30 p.m., ending an embarrassing episode that had tarnished the start of the school year.

"I instantly lost my headache," Interim Superintendent Robert C. Rice joked in an interview.

On the first day of school Wednesday, Rice canceled classes at Eastern and fired three officials, including the school's principal, after learning that the schedule of classes and room assignments had not been completed.

Without classes, teachers could not distribute instructional materials, and students stayed in homeroom working on reading, mathematics and science Thursday and yesterday.

Eastern, at 1700 East Capitol St. NE, will be open from 9 a.m. to 4 p.m. today and Monday to allow remaining students to pick up their schedules. A meeting will be held at 6:30 p.m. Wednesday in the school's auditorium to update parents on the school's new leadership and to address questions and concerns.

In the District, school scheduling is an intricate, labor-intensive process that requires experience and use of an antiquated software program. "It is partially manual and partially automated," Charles T. Thompson, the school system's chief technology officer, said.

High schools have the trickiest schedules, because of electives, variations in individual students' graduation requirements and internships and other outside activities for which students receive academic credit.

The computer system, People Oriented Information Systems for Education, takes about four hours to run schedules for every 1,000 students, Thompson said. That process had to occur three times before officials were satisfied that more than 95 percent of students, an acceptable minimum, were scheduled successfully.

Officials have not provided a full explanation of why the fired principal, Norman S. Smith Jr., did not complete the schedule on time, except to say that he did not fully understand the complex process or accept help that had been offered before the start of school. Smith, who was hired in August 2003, declined to comment yesterday. An assistant superintendent and a technology specialist also were dismissed.

At Eastern, the final scheduling was left until the last minute and data errors caused the system to malfunction Tuesday night, officials said. Thompson described the problem as: "Garbage in, garbage out."

Thompson conceded that the software system -- which runs on special hardware and is not compatible with such current operating systems as Windows -- is not fully reliable. The school system has spent $1.3 million on the first phase of a new student information system that will compile schedules and record grades and be operated at individual schools.

Rice praised a group of employees who have helped out at Eastern, including principals from other schools.

Academic officials who normally develop and oversee curriculum standards for the school system went to Eastern with makeshift instructional materials, since regular textbooks could not be issued. "They knew they had something to contribute," Rice said. "Quite frankly, they just got up and said, 'Let me go volunteer.' "

The eight specialists who produced the final schedule, according to Thompson, were Vincent D. Carter, Earl Douglas, Roszell Elam, Andre L. Fair, Vanessa O. Gaskins Harrison, Margaret Carter Hawkins, Andra James King and Michael Thompson.