BERKELEY, Calif. -- Charles Pierce leaped atop a concrete rail, slid down the back, then reappeared moments later at his father's side. Charles was a bundle of hyperactivity, as fidgety as thumbs on a Playstation game pad -- not the usual behavior for an upperclassman at the prestigious flagship campus of the University of California.
At 13, Charles is the youngest transfer student to enroll this fall at Berkeley -- certainly an achievement, but made all the more remarkable for the Pierce family because Charles's 14-year-old sister, Mayumi, transferred along with him. Both entered as juniors and if all goes well, they will get their degrees in two years -- before most of their peers are out of high school.
Mayumi is thinking about going into medicine. Charles, initially interested in science, is now considering a career in law.
''Whatever makes them happy," said their father, Wincie Pierce, who since the start of classes has been following closely behind his children, particularly Charles.
''Sometimes I have to poke him when his attention starts to wander," said Pierce, who sits in on classes with his son.
Mayumi is allowed more freedom. ''She's older. She can take care of herself," her father said. Besides, said Charles, she is embarrassed having her dad around.
Their father and their mother, Qin Ma, are Berkeley alumni.
''I hope that they won't have any bad influences from other Berkeley students," said Qin Ma. ''We have given them the foundation to know what's proper and not proper. We talked about drugs, alcohol, and sex. So far, all of the people, their fellow students and the professors, have been very good.
''Sometimes we get concerned about them because they're at the university. It's a pretty big campus," added Qin Ma. ''We're worried about two things: safety -- they're still pretty young -- and, secondly, their transportation and making sure they get to classes on time."
With a sprawling campus like Berkeley's, it's been tough, sometimes more challenging than the classes themselves, said Charles. It's a half-mile trek between two of his classes.
''He has yet to arrive to any of his classes on time," said his father.
It took dedication and hard work from the entire family to get this far, according to the couple, who began home-schooling their children after enrolling them briefly in public and Montessori schools.
''I have nothing against public school; I don't have anything against private schools. I thought I was the best one to teach them," said Qin Ma.
''We didn't think they would reach their potential by taking the traditional route," said her husband.
When the couple could no longer keep up with the children's academic needs, they began talking about enrolling them at Contra Costa College, a junior college in their hometown of San Pablo, just north of Berkeley.
Charles and Mayumi received their high school degrees by taking a proficiency exam, then enrolled at the two-year college. They spent three years at the community college, acclimating to the culture of higher academics before transferring to the university as juniors.
''It's a lot bigger here. I don't like that," said Charles, amid a blur of faces rushing through a campus courtyard. ''When you get out of class, there's so many people. There are 50 people in front of you, and you have to just stand there waiting for them to move."
Charles had another complaint: ''People aren't funny. They're too serious. All you see are people studying," said Charles, who lived in China with relatives until he was 3.
While still unusual, the number of youthful, nontraditional students gaining entry at colleges across the country is rising. UC Berkeley has hosted younger students before, but never sibling high-achievers as young as this pair.
In 1996, a transfer student enrolled two months shy of 13, according to university spokeswoman Noel Gallagher. The youngest freshman entered the university in 2000 at the age of 14 years and 5 months.
Do the siblings think they merit special attention? ''Not really," said Mayumi. ''There's about a few thousand other people who transferred here."
For the Pierce children, there are the expected rigors of academic life. But there are violin lessons, martial arts practice, and other responsibilities. When the schedule allows, there's time for video games and downtime at the computer.
''They know their responsibility," said Qin Ma, who met her husband while attending Berkeley as a visiting legal scholar from China. She later went on to earn law degrees from Boalt Hall.