Photo: Lynn Geter's mug shot provided by the Meriwether County, Ga., Sheriff's Department.
The 38-year-old faces one charge each of animal cruelty, child cruelty and battery.
Meriwether County sheriff Steve Whitlock told CBS affiliate WGCL that the 12-year-old boy told his teacher about the killing.
The Atlanta affiliate asked Whitlock, who knows the mother personally, if this is something that the son could have made up, but the sheriff says it happened.
"The mother was really upset and she proceeded to punish the child in a strange manner," Whitlock told the station.
Geter is a dental hygienist and a former daycare provider who used to care for kids out of her Warm Springs home, about 80 miles south of Atlanta. She has three kids including the 12-year-old son who came home from Manchester Middle School last week with bad grades.
A neighbor who's known the Geter family for almost 20 years can't believe it happened.
"I've known Lynn...Good people far as I'm concerned," Ken Brock told WGCL. "I'm not convinced of any of it."
The sheriff told WGCL that the mom has been arrested before for minor crimes, but nothing violent.
Geter was arrested last Friday. It was not immediately known if she had a lawyer.
Her children are now in the custody of the Division of Family and Children Services