The school was ranked second highest in Los Angeles County and seventh in the state by Newsweek and 26th in the state by the Washington Post for its college preparation.

On the national level, the school came in 79th according to Newsweek and 260th according to the Washington Post, when compared with public schools across the country.

School district officials were elated by the news.

"We are particularly proud that Diamond Bar, being a public, open-enrollment school, is still among the best schools around, near or far," said Principal Catherine Real in a statement.

To calculate its rankings, the Washington Post looked at nearly 2,000 public high schools across the country and added up the number of Advanced Placement, International Baccalaureate and other college-level tests each offered in 2010.

That number was then divided by the number of seniors who graduated that year at each school.

The formula Newsweek used to calculate its rankings was more complicated. It looked at 1,100 public schools and took into account six categories, including graduation rate, percentage of students who attend college immediately after graduation, the number of students who take A.P., I.B. or other college-level tests and how students scored on them, the number of college-level courses offered, and how students scored on the SAT and ACT tests.

Larry Redinger, a member of the Walnut Valley Unified Board of Education whose three daughters have attended the high school, said such an achievement would not be possible without support from both the community and teachers.

"I'd say I'm pretty excited," he said. "That school is really amazing. It's sort of like a private school on a public roster."

Redinger said he believes the school's high ranking is also due to its administrators striking a balance between academics, arts and sports, unlike some other schools, which may specialize in just one area.

"Why Diamond Bar? Because it's really balanced," he said.

Nancy Lyons, another school board member, called the school "the perfect three-legged stool," supported by students, parents and teachers.

"I'm extremely proud of Diamond Bar High School," she said. "In this era of decreased budgets and having to do more with less, we have teachers that can do more with less."

She said the high rankings for 2010 are also very much the legacy of now-retired Principal Denis Paul, who put policies in place that helped involve parents with school activities.

"He was the genius behind coming up with all these parents groups," she said. "Now there's eight separate parent groups supporting each other and supporting to school."

The district's other high school, Walnut High, also placed high in the Washington Post's rankings, coming in at 62nd place in the state and 522nd nationally. It did not appear in the Newsweek rankings.