District special-education advocates say that an incident this week in which a child was forgotten for hours in the back of a school bus highlights the broader challenge city officials face as they assume control of buses after years of federal court supervision.

Two employees of the city’s Office of the State Superintendent of Education, which oversees special-education transportation, were fired after leaving a special-needs preschooler alone for nearly seven hours Tuesday.

“This is an incident that is totally unacceptable and we want to make sure this never happens again,” Jennifer Lav, a University Legal Services lawyer who represents students with disabilities, wrote in an e-mail. “We plan to request an independent investigation and independent evaluation of any necessary corrective action.”

Lav represents plaintiffs in a class-action lawsuit brought in 1995 by D.C. parents who charged that the city had failed to provide reliable transportation for more than 3,000 students with disabilities.

The long-running suit, Petties v. District of Columbia, led to federal oversight of the city’s special-education school buses until earlier this month, when a federal judge agreed that the city had demonstrated that it can provide safe and consistent service.

The judge released the bus system from federal control and set a mid-December public hearing at which the case is expected to be dismissed. Every bus is outfitted with a Global Positioning System device, according to city officials, and 98 percent of buses get kids to school before the morning bell rings.

“We are proud of our record,” said Hosanna Mahaley Jones, the District’s state superintendent of education.

The 4-year-old was left alone Tuesday because of gross negligence by individuals who failed to observe established safety protocols, Mahaley Jones said. “That one incident doesn’t define our workforce nor does it define our operations,” she said.

David Gilmore, who served for nearly a decade as the supervising court master in charge of the city’s special-education buses, said the incident appeared to stem from “human error” and does not change his assessment that the city is ready to manage its own school transportation.

Advocates agreed that the city has made strides under the scrutiny of the class-action suit, but they said there is still more work to do. Judith Sandalow, executive director of the Children’s Law Center, a D.C. advocacy group, said that to ensure students are served well, the D.C. Council and the public need to “pay attention now that the court isn’t.”

Some parents of special-education students are unsatisfied.

Trenise Stitt, the mother of a 13-year-old nonverbal boy with autism, said her son TeYon is supposed to have a dedicated bus aide who is trained to communicate with him and safely deal with his behaviors. But the aides this school year have not been trained and twice this month called police to deal with her son, Stitt said. She said TeYon and an aide had hit each other, and she is no longer comfortable sending him to school by bus.

“I can’t constantly keep shipping my son on the bus if you are going to call the police,” she said. “What if he flips out so bad that the police can’t handle him, either?”She kept him out of school for a week before taking him to class Wednesday in a taxi that cost $23.90.

Mahaley Jones said that as the result of a two-week investigation into Stitt’s complaints, which wrapped up late Thursday, the superintendent’s office plans to take unspecified personnel actions Friday. The office also is going to meet Stitt’s requests for alternate transportation, which Stitt said includes private transportation.