Police spokesman Sgt. Robert Lachance says one bus rear-ended the other on the parkway at about 5:30 p.m. Friday.
He says the first bus was disabled, and that the door of the second bus was pinched closed and had to be opened by emergency workers.
Lachance says 12 teenagers suffered minor neck and back injuries, and seven of them were being treated at a hospital. He says their injuries appear to be non-life threatening.
WPXI television reported the teens were from Woodland Hills School District.
Lachance says the accident happened south of Route 123 and that traffic in the area was tied up for hours.