A charter school run by the United Federation of Teachers hired a new consultant this week after the principal raised the ire of parents by allegedly ordering a group of first-graders to clean up human waste in the bathroom.

The president of the teachers union, Randi Weingarten, apologized to parents at the school in the East New York section of Brooklyn on Tuesday night. The first-year principal, Rita Danis, also told the group of about two dozen parents that she was sorry.

Last month, Ms. Danis instructed four first-grade boys to tidy up the bathroom after she found them mucking it up. Two of the boys went home and allegedly told their parents that they had been forced to clean up feces.

“This is not something a 6-year-old should go through,” the mother of one the boys allegedly involved in the incident, Shalese Lucas-Chisholm, told an NBC TV reporter before the Tuesday meeting. Her 6-year-old son, Bijean, added, “When I was asked to do it, I felt a little unhappy.” Another parent said the incident had brought down her son’s self-esteem.

The school, which is publicly funded but operated by the union, disciplined Ms. Danis and explained that she should not have made the students clean the bathroom. She also was disciplined for failing to report the incident to the school’s board of trustees until November 22, about two weeks after it occurred.

“The school leader, who is an exemplary instructional leader, made two errors in judgment – for which the school is taking responsibility, and for which she has been disciplined,” Ms. Weingarten said in a statement issued last night.

She said she ordered an investigation immediately after learning about the incident; that investigation is still ongoing.

“We may never learn exactly what happened,” Ms. Weingarten said. “We think what happened is there were paper towels strewn in the boys’ bathroom. Some people think there was something under the paper towels; some people think there wasn’t. But the bottom line is this: Kids should not be cleaning up in a bathroom.”

There is no specific city policy about students cleaning bathrooms, but all forms of corporal punishment are strictly prohibited under state law.

This week, the school’s board of trustees hired a retired principal, Jeanette Reed, to advise the school leader. Ms. Reed previously served as principal for more than a decade in Brooklyn public schools.

The UFT Elementary School opened in September with 150 kindergarten and first-grade students. The school boasts of being the country’s first to be union-run.

Education policy-makers are keeping a close eye on the school to determine if a charter school can operate successfully under the constraints of a union contract. Charter schools typically are not required to hire union teachers and are exempt from most district rules. Some critics opposed granting the UFT a charter.

The UFT school recently received a $1 million donation from the Broad Foundation. The union has an application pending to open a second charter school, a high school, also in Brooklyn.