Karla Homolka served a 12-year sentence for the rape and murder of two schoolgirls in a case that horrified the country.
It emerged this week that she was helping out at her children's private school in Montreal.
Homolka, 47, was freed from a maximum security prison in Quebec in 2005.
CityNews reported this week that she had been helping supervise kindergarten students at Greaves Adventist Academy.
The Christian school has received a flood of complaints from parents and the public.
Homolka and her ex-husband, Paul Bernardo, killed Ontario schoolgirls Kristen French, 15, and Leslie Mahaffy, 14, in the early 1990s.
Homolka also played a part in the 1990 rape and murder of her 15-year-old sister Tammy.
But she was given a relatively light sentence in 1993 after agreeing to testify against Bernardo.
He received a life sentence for murder, kidnapping, forcible confinement and aggravated sexual assault, and remains in jail in Ontario.
After her release from prison, Homolka married her lawyer's brother and they have three children together.
The Seventh-day Adventist Church, which runs the Montreal school, announced on Thursday it had changed its policy on volunteers to exclude anyone with a criminal record.
"We have heard and listened to the concerns of parents and members of the community uncomfortable with recent reports in the media," the church said in a statement.
Earlier in the week, a spokesman for the church said they had been aware of Homolka's crimes.
A centre-left political leader, Thomas Mulcair of the New Democrats, was lambasted in the press for even daring to raise the question of whether Homolka deserved forgiveness.
Relatives of the victims do not believe she has paid her debt to society.
Tim Danson, a lawyer for the French and Mahaffy families, said on Friday that Homolka has not shown a "scintilla of remorse or contrition".
He said the school had neglected its responsibility to inform parents of her presence.
The Seventh-day Adventist Church operates 43 schools in Canada with 4,362 students in Canada.
One of Canada's most notorious child-killers has been told she can no longer volunteer at a primary school, amid nationwide uproar at news of her role.