A middle-school principal struck a high school student with her SUV at a crosswalk Monday and stayed at the scene with emergency crews, but didn't identify herself as the driver until calling authorities 50 minutes after the accident, police said.

The 15-year-old Pennridge High School student suffered head injuries and was in critical but stable condition at Lehigh Valley Hospital, Pennridge Regional Police Chief David A. Mettin told The Associated Press. He did not release the student's name.

Margaret Kantes, 66, struck the student at an intersection at about 6:50 a.m., parked her SUV and stayed near the scene, the chief said. She twice started to call 911 but was told by someone else that they already had reached emergency dispatchers, he said.

Kantes left the scene by the time Mettin arrived at about 7:15 a.m. and apparently drove a few hundred yards to her parking spot at Pennridge North Middle School, the chief said. She called police at about 7:40 a.m. to report that she was the driver, Mettin said.

At the time, police were investigating reports that a school bus was involved in a suspected hit-and-run.

"She never said (at the scene), 'I'm the driver.' We'll find out about that," Mettin said. "We do want to take a look at her car."

Kantes appeared to have a green light at the intersection, he said. She voluntarily submitted to a blood test and is not under arrest.

"I know she was very shaken up," Mettin said.

Messages left with school district officials and at Kantes' home in Doylestown, about 25 miles north of Philadelphia, were not immediately returned.

The SUV has been impounded as part of an investigation that is expected to take several days or more. The speed limit in the area is 35 mph, but 15 mph during school hours, which should have been in effect, the chief said.