Angela Hassan, formerly Deeney, was found guilty of three charges following a trial at Hamilton Sheriff Court on 15 October 2024.
The 78-year-old, from Motherwell, targeted the victims between 1971 and 1990 after they were placed in her care.
The children were aged between five and 11 when the abuse began.
Hassan’s offending was discovered following police enquiries into allegations of child abuse at Smyllum Park orphanage in Lanark.
One of Hassan’s victims had spent time at the institution before going to stay with the foster carer at her then-home in Wishaw.
Hassan used cruel and unnatural treatment towards the girl, which included striking her head against a wall and repeatedly punching her on the head and body.
In addition, she humiliated the child by forcing her to put used sanitary towels into a coal fire in front of other people at the home.
A young boy was also subjected to repeated violent attacks by Hassan, who hit him with a slipper, a branch and a belt.
On various occasions, she held the child down and forced food into his mouth as well as humiliating him after he wet the bed.
Hassan’s third victim was also physically abused and humiliated, with the carer telling her she did not need sanitary products.
On 15 November 2024, as a direct alternative to custody, Hassan was given a Community Payback Order with a requirement to complete 300 hours of unpaid work within 15 months.
She was also placed under supervision for the same period of time.
Les Brown, Procurator Fiscal for South Strathclyde, said: “Angela Hassan exploited her position of trust to abuse vulnerable young people, who should have been safe in her care.
“Instead, she inflicted unimaginable trauma through her violent and cruel offending over a significant number of years.
“It is thanks to the bravery and strength of the victims giving evidence that this conviction has been made possible.
"COPFS remains committed to prosecuting those responsible for abusing children in care settings – regardless of how long ago the offending took place.
“I would urge any victim of similar crime not to suffer in silence but to report it. You will be listened to as we use all the tools available to use to seek justice.”