It happened just before 4 p.m. at the Heston School located on 54th Street and Lansdowne Avenue in West Philadelphia.
Police say a 21-year-old man was shot in the upper thigh near the school building. He was taken to an area hospital and placed in stable condition.
A spokesperson with the Philadelphia School District says bullets came through the window of Edward Heston School.
"I want to say that three school district employees are lucky to be alive this evening. Gunshots were heard in this neighborhood. Three bullets came through the window of the main office of Heston School. This is totally unacceptable to fire shots anywhere in the city, especially so close to where school children are," said Deputy Chief of Communications Monique Braxton.
"She heard the bullets whiz by - that's how close it was to her - and two other people were also standing in the office at that time," added Braxton.
A bullet also pierced a neighbor's apartment window across the street.
"Glory be to God, I thank you because it could have been a disaster," said Priscilla Brewington.
Brewington lost a son to gun violence in 2009 - and is calling for the shootings to stop.
"My granddaughter doesn't have a father and it's just senseless," she said. "You get these guys and you ask them why - they wouldn't even be able to give you an explanation of what they're doing it for."
Officials say no children or employees of the school were injured.
The school was dismissed 45 minutes before the shooting occurred.
No arrests have been made at this time.
Anyone with information is asked to call police at 215-686-TIPS.
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