The idea came to Principal Barbara Liess last month when a rocking chair broke beyond repair at her Maryland elementary school and was hauled to an outdoor space on a school loading dock.

Liess decided the old piece of furniture could be useful in another way — as a target in a kind of “smash space.” Her staff could wield baseball bats and hack away at the chair to relieve tension.

“I got the idea after reading some business articles that discussed companies providing items to be smashed as a way to reduce stress,” Liess wrote this week in a message to families. She has been principal of Kensington Parkwood Elementary School in Montgomery County since 2007.

After her actions came under fire in recent days, Liess apologized Wednesday for her March decision, saying there was “no excuse” and calling it a “lapse in judgment.”

“I absolutely regret my decision to provide staff with an opportunity to ‘smash’ the rocking chair,” she wrote in the message. “This decision was not in response to any teacher comment or behavior, rather a misguided attempt by me to provide staff with an outlet.”

The specter of schoolteachers bashing furniture with bats on campus surfaced in a parents’ online discussion group Tuesday. One parent had heard a rumor at the bus stop about a “smash space” and asked others about it in disbelief.

PTA President Jessica Chertow confirmed the rumor and messaged the discussion group late Tuesday with details she gathered. Some of the bats were wooden and at least one was metal, she said, and a sign was displayed suggesting the wearing of goggles and closed-toe shoes. “Smash away,” it read.

Though it was unclear how many people participated, she said, no children were harmed or, as far as she knew, had heard or seen any chair-busting clatter.

Chertow called the idea “an example of a major lapse in judgment by Ms. Liess — despite good intentions.” She told school families that district officials were looking into the matter and “working hard to find the best path forward.”

Not everyone in the discussion group saw it as a major concern, but a number of parents voiced shock and disappointment, according to several who followed the discussion. And some questioned why the principal would urge teachers to respond to their stress with physical aggression when children are regularly told to “use their words.”

Montgomery school officials said they are continuing an investigation of the incident, which they said began in March.

Sarah Sirgo, a director of elementary school support and improvement for the district, told families in a message that the district “does not condone this behavior by our staff” and has long been committed to “providing its employees with wellness support to help staff manage stress.”

The smash space no longer exists at the school, said schools spokesman Derek Turner, and he did not have details on how long it was in use or how many staff had participated. He said Liess, the principal, had no further comment.

One father, who declined to be quoted by name because of the situation’s sensitivity, said he was concerned that anyone would think of creating such a space in an elementary school. As word spread this week, his child asked him why teachers at the school needed a smash room.

He said he thought that the incident unfairly cast a poor light on educators.

“I truly do not believe our teachers are angry or frustrated,” he said.

Sheila O’Connell, a mother of three children and a parent at the school since 2009, said she hopes the school system takes its investigation seriously. The school’s teachers “do an excellent job” of teaching children how to manage conflict, she said.

“For an administrator to turn around and offer an inappropriate way to deal with conflict to the very same people who are guiding our children on a daily basis is disturbing,” she said.

As a parent, she said, “I don’t want my kids to feel this is an acceptable way to work out your problems. I thought we were teaching our children not to use violence.”

In her message this week, Liess said the school’s staff is committed to modeling appropriate ways for handling stress. “I recognize,” the principal said, “that while well-intended, this scenario is counter to what we teach students and has no place in a school.”