Exline said she does not really notice the age gap between herself and her 17- and 18-year-old peers－and neither do they.

"I didn't tell people right off the bat that I was 15," she said. "A lot of people were pretty surprised."At 8 years old, she was already in sixth grade. By 13, she had finished high school math. She turned 15 in February and graduated a few months later.

Exline excels at math and science and is interested in politics, so she enrolled in a program that will award her degrees from both the engineering and liberal arts schools when she graduates.

"Her motivation, discipline and maturity provided clear evidence that, despite her age, she was ready to ... thrive in Penn's rigorous academic environment," Eric Kaplan, interim dean of admissions, said.

There have been much younger college students: Jessica Meeker enrolled at Penn State two months before her 13th birthday, graduating in 2004 at age 16.

Exline's mother, Chyrese, said her concerns about her daughter's freshman year are probably no different from any other parent's. "We did our best to prepare her," she said.