It has happened again. Another lost student. Another bus driver dropping a Kindergarten student off with no adult there in violation of division policy. For school officials, another black eye.

"It’s just unacceptable," said Vice Mayor Kerry Donley, adding that he would like to see some personnel accountability. "We can no longer say it’s acceptable to sign a pledge and check some badges. This can’t go on."

The problems began at Mount Vernon Community School, where a Kindergarten student boarded a bus he was never supposed to be on and ended up wandering the streets of an unfamiliar neighborhood lost and afraid. Then a Lyles-Crouch Elementary School student was allowed to get off a bus even though her mother had not yet arrived at the bus stop, leaving the child upset and locked out of her own house until the mother returned. Last week, a George Mason Elementary School student boarded a bus instead of going to an after-school program where she was expected.

"Our incident involved a substitute teacher," wrote George Mason Principal Dawn Feltman in an e-mail to parents. "I have personally investigated and taken appropriate action to ensure that we have better communication with our substitutes in the future."

In response to the three incidents, the school system has started placing a "K" sticker on each Kindergarten bus rider so drivers know which students are in Kindergarten — and, therefore, which are required to be met by an adult at the bus stop. Feltman said that she has taken an additional step, creating a list of all Kindergarten students who are bus riders. She said that will allow the school’s staff to double check that all Kindergarten students are wearing stickers and seated at the front of the bus.

"Obviously, we are all concerned about this because when a Kindergartner gets off the bus and nobody is there to greet them, there is a potential for something to happen," said Ann O’Hanlon, president of the George Mason Elementary School PTA. "Thank God that hasn’t happened with any of these incidents."

SCHOOL ADMINISTRATORS have taken a number of steps to prevent further problems since the first incident happened in early October. The first change was reformatting attendance data so that transportation information was presented on the same document as class information for each child. Then the division’s transportation officials installed a series of animal logos on each school bus to create a sense of identity, encouraging students to take more of an active role in remembering which bus they are supposed to board.

Last week, Superintendent Morton Sherman sent a letter to parents responding to the first two incidents. In the letter, Sherman explained that all bus drivers have now signed a letter of procedures affirming that they will not drop off any Kindergarten student unless a parent or designated adult is at the bus stop. The superintendent also used the letter to announce the creation of a new work group to revise procedures for arrival and dismissal. The work group will consist of parents, teachers, bus drivers, administrators and after-school child-care providers.

"Disciplinary action has been taken where appropriate and some procedures at the schools have been changed as a result," Sherman wrote. "We will do everything necessary to make sure all students are properly supervised and transported at all times."

NONE OF THESE steps seem to have been able to prevent the third incident from happening, prompting some to question how the school system has responded to events. Rodney Salinas, whose son was the Mount Vernon student that was dropped off in an unfamiliar neighborhood, has been critical of the school system’s actions. He criticized the animal logos as a mistake because it put more responsibility on the children rather than adults, and he said he was disappointed that his recent appearance at a School Board meeting didn’t prompt more of a dialogue.

"There is a growing crisis of confidence in the school system among parents in Alexandria," said Salinas. "If ACPS continues to treat these cases in the lackadaisical manner as it has over the past three weeks, it is only a matter of time before a child is seriously hurt."

School Board chairwoman Yvonne Folkerts said that she hopes the measures Sherman has already put in place will prevent future problems.

"We’re moving thousands of kids each day, and mistakes are going to happen," said Folkerts. "I hope that the measures the superintendent has put in place are going to work, but if they don’t we’re going to have to ask him to do more."