According to an incident report obtained by The Chronicle on Friday, the attack happened as the 13-year-old brought his 12-year-old brother to the teacher's class to confront another student.
As the two brothers approached the student, the teacher stepped between them "and immediately began being struck in the stomach and arms by (the 13-year-old) offender."
According to the report, the 13-year-old, whose name is blacked out, left his class to get his brother, and when they entered the pregnant teacher's room she asked them to leave, "but they refused."
After being struck, the teacher, whose name also was redacted from the report, pushed the brothers out of the class and they were taken to the school office.
Officials have said the teacher was examined by a school nurse and instructed to see her physician. She was on leave for three school days after the incident, but school officials have refused to comment on the condition of her baby.
Initially, the school system's safety office wasn't notified by the school's principal, who said he reported the case to the school system's central office.
After hearing about the incident from a Chronicle reporter five days later, school safety Lt. Richard Roundtree initiated an investigation to determine whether criminal charges were warranted.
He said at the time that his office prefers to be called in immediately any time a teacher or student is injured.
The 12-year-old didn't strike the teacher, school system spokesman Louis Svehla said. Criminal charges can't be filed against a student younger than 13, he said.
Both special-needs students, he said, were suspended pending a tribunal, which was held earlier this week. Officials have said the results of that tribunal can't be released until after a 10-day period that allows for an appeal.
It's now up to the state juvenile justice department to determine whether the 13-year-old should be taken into custody on the charge, Svehla said.
"The physical paperwork will be delivered to juvenile justice Monday morning," he said. "Then they have up to 72 hours to decide what to do."
Aggravated battery is a felony, according to the Georgia Department of Juvenile Justice. Georgia law states that "a person commits the offense of aggravated battery when he or she maliciously causes bodily harm to another by depriving him or her of a member of his or her body, by rendering a member of his or her body useless, or by seriously disfiguring his or her body or a member thereof."
A juvenile convicted of the charge could face a maximum sentence of being incarcerated in a juvenile justice center until the age of 21, Svehla said. He said the school system isn't releasing details as to why it chose to pursue an aggravated battery charge.