Daniel Chen juggled an average course load at Head-Royce School, a private K-12 hills school. He studied each day. He practiced the viola each night.

Oh, and he also ran a sushi business.

Called Sakana Sushi Catering Business, 18-year-old Chen, who graduated Sunday, started the company with two friends in the eighth-grade.

They were tired of the same lunchroom offerings, so they started their own business. It quickly boomed. Fifty to 70 students lined up for the fare, he said.

"We had huge lines -- we had to do a pre-order sign-up," said Chen, who lives in Orinda.

The friends soon expanded the business into catering events when they had time. They had a first-hand look at the business world, something Chen plans to continue with a mixture of economics and architecture courses at Harvard University this fall.

The friends behind the sushi business also learned something about charity. The business went bankrupt for a good cause this year, when they donated all their profits to Oakland Children's Hospital in the name of a classmate who died.

When he wasn't busy with studies or business, Chen practiced the viola and was a member of the San Francisco Youth Orchestra.

"They run it like a professional orchestra," Chen said. He'll travel in July throughout Europe to perform with the orchestra, he said.

All in all, Chen looks back on his years at Head-Royce with fondness, he said. He started in the first grade and at one point tried to switch to a different school. But he's glad he stayed.

"I've made some really good friends here," Chen said.