The principal of St. Clare of Montefalco Catholic School had students stay after a Mass last month and informed the fifth- through eighth-graders that she has a zero-tolerance policy for cursing.
Just in case anyone was not sure what she was talking about, Avery read off a list of the very words and phrases that she was banning.
"It got a little quiet in church" during her talk, she told the Detroit Free Press.
Some parents were shocked, but others applauded, the newspaper said.
"In a way you would think a nun would shy away from something like that, but she's very open with the children, very clear in her messages," said Margaret Roache, chairperson of the school commission.
Roache's sixth-grade son was there when Avery read the list of banned words.
"When I asked him to give me a sample of it, he said 'Oh, no, I can't say it!"' Roache said. "I thought it was great."
A representative of the Archdiocese of Detroit declined to comment Sunday.
Curse words are not the only things that set Avery off. She has also banned the words "stupid" and "boring."
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969