A sell-out crowd cheered Bryant in the gym at Lower Merion High School. He arrived late because of an early snowstorm that fouled traffic in the area, WCAU-TV reported.
Bryant donated $400,000 to the school for arts and athletic programs. Money from Thursday night's event will also go to the school.
The audience included Bryant's teammates with the Lakers.
"For me, it's really about helping the next generation," Bryant said. "This is where I came from, this is where I grew up. I didn't go to college, so this is my university."
Bryant, the son of Joe "Jellybean" Bryant, who played for the Philadelphia 76ers, had a spectacular high school career. He went directly to the Lakers in 1996 as the first guard to go to the NBA straight out of high school.