A Georgetown, Massachusetts, preschool is causing controversy by banning students from using the term "best friend."

WFTXT reported that mother Christine Hartwell said she is outraged after a teacher at Pentucket Workshop Preschool told her 4-year-old daughter she couldn't call one of her classmates her "best friend."

The preschool defends its stance, saying banning the term promotes inclusion in the classroom, while Hartwell said it can end up having a negative affect on her daughter.

“How do you police a 4-year-old from expressing their feelings?” Hartwell told WFXT. “It’s outrageous. It’s silly (and) it hurts.”

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Hartwell said she first learned of the ban after her daughter Julia came home from school one day acting differently. Julia told her mother she was upset because her teacher told her she couldn't call one of her classmates her best friend.

“When I asked her what was wrong, she said she was really sad about what her teacher did that day,” Hartwell said.

Hartwell said her daughter is now hesitant to call anyone her best friend, adding that she and her husband went to the director at Pentucket Workshop to find out more about the policy. Hartwell said it’s not spelled out in the school handbook.

The preschool sent a letter to the Hartwell family in response to the issue, saying they’ve done research on the pros and cons of using the term best friend, and that they’ll continue to discourage children from using it in group settings.

“It has been our experience (which spans decades) that the use of the term ‘best friend,’ even when used in a loving way, can lead other children to feel excluded (...) which can ultimately lead to the formation of ‘cliques’ and ‘outsiders,’” the letter said in part.

Hartwell said having a best friend allow a child to feel more secure at school, and she is removing Julia from the preschool to find a new one where her daughter can still call someone her best friend.

“I want her to be able to express her thoughts and feelings in a healthy way, as children should,” said Hartwell.

The school said it has no comment on the issue.