City police were called to Dieruff High School about a possibly armed student around 10:30 a.m., the department said in a release.
A school resource officer and responding APD officers eventually located the student, "who had been in possession of a firearm on school property," authorities said.
The 17-year-old was charged with possession of a firearm with an altered serial number, possessing a firearm as a minor, and unlicensed carry, APD said.
He will be tried in Lehigh County Juvenile Court, they added.
It's a familiar incident for school administrators in Allentown: in September, a William Allen High School student was found with a loaded gun in a boys' restroom, and last November, Dieruff was evacuated due to a violent threat that was later discredited.
Daily Voice has reached out to Allentown School District for comment.
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