Students at Academic Magnet High School take Advanced Placement exams seriously.

About 400 of the school’s nearly 620 students studied for more than 1,000 of the rigorous tests last year, and 78 percent earned passing scores. On Tuesday, some calculus students were so engrossed in a three-plus-hour AP practice exam that they ignored the pizza slices on their desks at lunchtime.

“(Teachers) do whatever it takes to get their kids ready,” said Principal Judith Peterson.

Students’ success on those tests is one of the factors U.S. News & World Report magazine considered when evaluating more than 21,000 public high schools in 49 states.

Charleston County’s flagship Academic Magnet High School jumped 17 spots this year to No. 10. It was the top rated school in the state, and the No. 2 magnet school in the country.

Here’s what you need to know about these latest rankings:

How are schools ranked?

The methodology looked at three key criteria for each school: overall performance of students on state tests, the most disadvantaged students’ performance compared with the state average, and students’ participation rate in and performance on AP or International Baccalaureate exams. This is the same methodology as last year.

Is this first national ranking?

No. U.S. News has published a list of the country’s top high schools five times since 2007, and Academic Magnet High has ranked in the top 30 every time. Before this year, it ranked No. 27 twice, No. 9 and No. 12. Newsweek magazine also publishes a list of the country’s best high schools, and Academic Magnet has ranked among the best; it came in at No. 22 last year. The Washington Post also recently published the country’s Most Challenging High Schools, and Academic Magnet was No. 32.

Why so successful?

The magnet school in North Charleston accepts students from across the county through a selective admissions process. Students must take a minimum of four Advanced Placement courses to graduate. Peterson attributed the school’s success to students who are eager to learn, strong parental support and strong teacher-to-student relationships.

Others?

Yes. Charleston County School of the Arts received a gold award, which was given to the country’s top 500 schools based on college readiness. The school ranked No. 2 in the state and No. 457 nationally.

Wando High School earned a silver award, which was given to 1,790 schools. Wando was No. 16 in the state and No. 1,687 nationally.

Bronze awards went to 2,515 schools for high performance based on state exams. Cross High, Military Magnet Academy and Timberland High were recognized with bronze awards.

Proud

On Tuesday, many students and teachers were aware of the No. 10 ranking and were glad it improved, but they seemed to be going about business as usual.

“We’re proud,” said Cathy Woods, an Advanced Placement English teacher, who said the school hadn’t changed what it was doing from last year. “It’s just the same great program.”

Reach Diette Courrégé Casey at @Diette on Twitter or (843) 937-5546.