The stabbing happened outside of school hours during a fight between the boy and the teenager on Saturday, police say.
The fight occurred at Bucher Elementary School in Manheim Township, Lancaster County, just after 7 p.m.
The suspect, a 13-year-old boy was fighting with a boy,11, when he "grazed the other in the stomach with a knife," police said in a statement.
The 11-year-old victim was treated at an area hospital and released.
The identities of the two involved will not be released.
There is no word on any criminal charges.
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