That knife passed through a metal detector but was not detected.
"There is a metal detector here. Why did it not pick up the knife and alert the officer of school safety and climate managers who were close by? We don't know. The office of school safety is currently investigating this particular metal detector," said Philadelphia School District Spokesperson Monique Braxton.
The stabbing happened around noon at Castor Gardens Middle School on the 1800 block of Cottman Avenue.
School workers say there was an altercation with the student that left two of them stabbed and wounded.
There was a lockdown for a short time on Tuesday and families were notified of the incident. No students were injured in this incident.
"My 11-year-old daughter called me, talking about there is cops and a stabbing," recalled Jessica Santos.
"I just see the message and we worried about it. We don't know what's going on," added Jaclyn Sosa.
Police say the student pulled a knife out of his bag while inside a classroom.
"The other students notified the teachers. Two of the aides went over and disarmed the student. While they did that they were cut superficially," said Deputy Commissioner Frank Vanore.
The victims are a 31-year-old woman and a 63-year-old woman. Police say they suffered cuts to the arm and stomach. The principal described the injuries as "minor."
Both staff members have since been treated and released from the hospital.
The incident left parents on edge.
"There's no protection for our kids in the Philadelphia School District," said another concerned parent.
The 11-year-old has developmental issues, police say, and officers are working with his parents.
"I think in this case we have to give this young man some grace. He is a minor. As the police have told us, he has some special needs, special circumstances," Braxton said. "The good thing about all this is that both employees suffered non-life-threatening injuries and they're going to be fine. Everyone was terrified, including the student that had the knife."