On Monday, Hogan charged the grandmother, 56-year-old Pauline Bilinski-Munion, with child endangerment and drug offenses. He also lashed out at school administrators.
"We're lucky we don't have a dead 7-year-old on our hands," Hogan said.
James Ellison, the school district's solicitor, said officials did call law enforcement: the district's police department, the Caln Township police, and the Coatesville city police.
"We typically report crimes to the local police, and that's exactly what we did here," Ellison said.
The dustup was the latest between Coatesville school officials and the district attorney. Ellison said the response to the heroin discovery was not affected by his own tense relationship with Hogan, who has accused him and members of the school board of trying to intimidate witnesses cooperating with the county's investigation following last year's racist texting scandal. Ellison is also being investigated by Hogan's office as possibly overbilling the district.
Acting Superintendent Leonard Fitts did not return a request for comment left Monday with his secretary. Caln Township's police chief, Joe Elias, also could not be reached for comment.
On Friday, a teacher overheard that a student had drugs at school, approached the student, and found nine small bags of heroin stamped "Victoria Secret," officials said.
Ellison said the staff who confiscated the drugs asked students if they had seen any more. None said they had. Hogan and Ellison were both unsure if the student who later came home with a heroin packet was in the same class as the child who brought the drugs.
Ellison said the police confirmed that the drugs were heroin about 3:30 p.m. and notified parents in an automated message later that day.
He was unsure what time the call went out. Hogan said it was not until about 9 p.m.
The voice message said a dangerous substance - it did not specify heroin - had been found at school and asked parents to see if it had been distributed to their children.
"If it is in their possession, please take it immediately to the local police," the message said. "As a precautionary measure, we also recommend that you immediately take your child to the closest hospital emergency room for a medical evaluation."
Hogan said the message effectively tipped off Bilinski-Munion, whereas his office did not learn of the case until Saturday, when it was too late to respond.
"This is a full-scale emergency when you have heroin loose in a grade school classroom," Hogan said. "There is no way that kid would have been able to get out of that classroom with a bag of heroin if they responded appropriately."
Detectives found and interviewed family members of the child who brought the drugs to school. Officials said Bilinski-Munion had been watching her grandson on Thursday at the family home on Woodland Avenue in Modena when she brought heroin into the home and lost track of it.
Carl Holmes, chief inspector with the Philadelphia Police Department's office of school safety, said that if drugs were found in a city elementary school classroom, one of his first calls would likely be to 911.
"Some drugs can be ingested through the skin by touching them. Heroin is one of them," he said. "We don't know what the substance is, and we don't know what kind of effect it's going to have on a child."
What should be standard procedure is communicating openly with parents in the midst of a safety threat, according to Ron Stevens, executive director of the National School Safety Center. He said he was struck that Coatesville school officials did not tell parents exactly what kind of danger to look for.
"What was it?" Stevens said. "An explosive device? A particular kind of drug, or hazardous material? Or weapon?"
Ken Trump, president of National School Safety & Security Services, a consulting firm in Ohio, said he often suggests that schools send out a message to parents alerting them to the discovery of "suspected drugs" instead of waiting for test results that confirm the substance.
"You can't lose anything by being overly communicative vs. under-communicating in a situation like this," Trump said.
Brittany Jacks, the parent of a 7-year-old student at the Caln Township school, said she did not receive the school district message Friday night and saw the warning Saturday after someone had posted it on Facebook.
Her son, Kamai, is autistic, so Jacks said she was unable to ask him if he had come into contact with the dangerous substance mentioned in the note. She said she did not even know that substance was heroin until she called the prosecutor's office Monday.
"I couldn't get any information from [Kamai], which led me to contact the school in a panic," she said. "Because I don't know if my child has seen it our touched it."