A Canadian serial killer who was jailed for the rapes and murders of three teen girls - including her sister - in the 1990s has been spotted volunteering at her children's elementary school.

Karla Homolka served 12 years in prison after being convicted in 1993 of raping, torturing and killing schoolgirls Kristen French and Leslie Mahaffy with her then-husband Paul Bernardo.

She also played a role in the death of her 15-year-old sister Tammy after she helped Bernardo drug, rape and ultimately kill her.

Homolka, who split from Bernardo while in jail, was released in 2005 and married her lawyer's brother Thierry Bordelais.

Canadian serial killer Karla Homolka who was jailed for the rapes and murders of three teen girls - including her sister - in the 1990s was spotted outside (above) her children's elementary school in Montreal this week

Homolka (pictured in 1993) was jailed for 12 years for the rape and murder of the three teenage schoolgirls in the early 1990s

The 47-year-old, who has three children from her second marriage, now sometimes volunteers at the private Christian school in Montreal where her kids are enrolled.

She was pictured outside Greaves Adventist Academy by the Montreal Gazette this week - much to the outrage of concerned parents.

The convicted killer recently helped supervise a group of kindergarten students during a field trip, and on another occasion was invited into a classroom to show the children how to knit, City News reports.

Homolka also brought in a dog for a show-and-tell class and has been seen dropping and picking her children up from the school.'We don't want her here,' one parent said. 'How would you feel knowing that your child is interacting with a person who is a serial killer? It's not right.'

Homolka was convicted in 1993 of raping and killing schoolgirls Kristen French (left) and Leslie Mahaffy (center). She also played a role in the death of her 15-year-old sister Tammy (right)

Karla Homolka was convicted in 1993 of carrying out the murders with her then-husband Paul Bernardo (above). He is serving an indefinite sentence for the brutal killings

A Seventh-day Adventist Church spokesman said the school board was fully aware of Homolka's history.

'She is not a regular volunteer and can never be alone with any children, either in school or churches,' the spokesman said.

'It is protocol for all of our schools across Canada, and most of the world, to do background checks, not only on teachers, but volunteers as well as clergy.

'As I said, she is not a regular volunteer. Rarely would she have cause to go into the school, and when she is, she is never alone.'

Homolka lived in Quebec immediately after she was released from jail, before moving to the Caribbean with her children to avoid media scrutiny.

A Seventh-day Adventist Church spokesman said the school board at Greaves Adventist Academy (above) was fully aware of Homolka's history

Homolka dodged photographers outside the private Christian school this week

Homolka struck a controversial plea deal in the 1990s in which she pleaded guilty to manslaughter to have her sentence reduced to 12 years

She has been living in the Montreal suburb of Chateauguay for the last two years.

The murder trials of both Homolka and her then-husband Bernardo were high-profile cases in the early 1990s.

Homolka struck a controversial plea deal in which she pleaded guilty to manslaughter to have her sentence reduced to 12 years.

She had claimed that Bernardo had abused her and forced her to murder the teenage victims. Video footage of the crimes that surfaced later showed Homolka as a more willing participant.

Homolka was convicted of manslaughter for her role in the slayings of French and Mahaffey. She wasn't charged in the death of her sister but her sentence took the incident into account.