Hundreds of attendees and players were evacuated and at least one of the victims was taken to a hospital after shots rang out just before 8 p.m. at Marcus Foster Memorial Stadium, Philadelphia's FOX 29 reported.
The victims were 15 and 14 years old, police told the station.
The stadium is the home field for Simon Gratz High School.
Simon Gratz was playing against Imhotep Charter High School. Imhotep was leading 19-0 at the time, with about 8 minutes remaining in the first half, the Philadelphia inquirer reported.
"Everybody ran out of the stadium," Imhotep coach Nick Lincoln told the newspaper, referring to the spectators. The players and coachs head toward the teams' respective locker rooms.
There was no immediate word on any arrests. Both shooting victims were in stable condition at Albert Einstein Medical center, FOX 29 reported.