WINDSOR, Ont. - In what the judge described as ''a parent's worst nightmare,'' a 15-year-old girl was sentenced yesterday to two years' probation for sexually assaulting the children she was babysitting.

Justice Saul Nosanchuk ruled that probation, under strict conditions, was the best hope for all concerned.

''I don't think, in 1999, to send a 15-year-old into custody for three to nine months in a case like this is the most humane or sensible thing to do,'' said Judge Nosanchuk.

The abuse took place between November, 1997, and February, 1998, when the adolescent babysat for three families in Amherstburg.

The teenager pleaded guilty to three counts of sexually assaulting two four-year-old girls and one six-year-old girl. The assaults included groping the children, inserting her fingers into their genitals, slapping, kicking and threatening to cut off the hair of one child if she did not comply.

As the girl, who was 13 when the crimes were committed, sat crumpled and weeping between her parents and her lawyer, the parents and grandparents of her victims came to the stand to denounce the teen and her family. Neither the girl nor her victims can be identified under terms of the Young Offenders Act.

''We trusted her to babysit our children,'' said one father. ''I paid her money to come into my home, so this little girl could sexually abuse my own daughter ... You tell your kids, don't worry, daddy will take care of you. And here I was handing my daughter to someone to sexually abuse.''

A mother of another victim said her daughter had gone from a happy child to one who ''throws fits'' and does not trust family or teachers.

''I have such anger toward the parents,'' she said. ''Where's your decency? Why don't you move? Don't look at me like that. You have no conscience.''

Defence lawyer Paul Esco told the court the girl had been sexually assaulted herself by an uncle when she was seven years old. ''Nothing was done about it because she didn't ever complain,'' he said.

A letter from the parents was read in court stating: ''We realize our daughter has a problem. What she did was horrible. She needed help but we didn't know where to turn.''

The girl's mother rose to apologize. She noted she was the one to inform her daughter's babysitting clients there was something wrong when the stories of sexual abuse began to surface. But she felt guilty and embarrassed.

The two years' probation, strict curfew conditions and mandatory counselling did not sit well with the parents of the victims.

''She gets 24 months, my daughter suffers the rest of her life,'' said one father. ''If she's a risk, why is she on the street?''