A day after the city eliminated dozens of school bus routes, the public advocate yesterday urged education officials to reconsider the move, calling the changes reckless and unsafe.

The letter to city schools Chancellor, Joel Klein, came after hundreds of students were stranded and parents were worried their young children would not be safe on public transit.

The new plan changes pickup times for tens of thousands of children. Some youngsters who once relied on school buses to get to class were instead given fare payment cards to take buses and the subway.

Public Advocate Betsy Gotbaum said her office had received similar complaints from parents. One child was scheduled to be picked up for school 18 minutes after the start of classes, she said.

A Department of Education spokeswoman, Margie Feinberg, said such experiences were not representative.

“Most of the students have traveled to school without incident over the past two days,” she said. “We will work to resolve every family’s problem as quickly as possible.”

In her letter, Ms. Gotbaum blamed the changes on what she called the department’s “no-bid contract with Alvarez & Marsal, a firm with an alarming track record in other school districts.” The city should “terminate A&M’s contract,” she wrote.

Ms. Feinberg called that “silly,” saying that the disruptions were no different than those experienced on the first day of school and any time there is a service change.