Schools Superintendent Elizabeth Morgan attributed the showing to teamwork at every level.
"This hasn't happened by accident," Morgan said. "I have to commend the teachers, principals and students. It's a lot of hard work."
"We're very pleased with our progress," Harrell said. "About five times as many seniors are taking the AP than 10 years ago."
Harrell said the number of students who took the International Baccalaureate tests increased over the last year, as well.
The International Baccalaureate is a two-year program that prepares students for college-level work. The curriculum includes English, a second language, social science, experimental science, mathematics and, typically, fine arts.
Students in the International Baccalaureate program are graded on a scale of 1 to 7. Students must score 4 or higher to pass.
Harrell said the school system has offered students the International Baccalaureate program for the last four years.
Twenty-four students took the International Baccalaureate program the first time it was offered during the 2006-07 school year, according to school system documents. That number increased to 32 in the school year that ended in 2009.
Harrell said Advanced Placement and International Baccalaureate are among the most challenging classes that high schools offer.
"The best way to prepare students for college is to let them take college courses their senior year," Harrell said.
Some colleges and universities offer credit to high school students who score a 4 or 5 on the Advanced Placement tests, Harrell said. Others will accept a 3.
"It's a huge incentive (to take the test)," Harrell said. "We're pleased with our progress in getting our students to take rigorous classes."
Morgan said students can earn close to a semester's worth of college credits during their high school years by scoring well on AP exams. As a result, students hit the ground running when they go to college.
"Students can start advancing themselves right from the beginning," Morgan said. "It does save money if you're exempt from some of those lower-level (college) courses."
Morgan said more students are taking tougher courses because principals and guidance counselors have been pushing the curriculum.
"I think AP to me represents opportunity and exposure to all of our students," Morgan said. "They have to work harder and that's what we want to see."
The Advanced Placement tests have been offered in Washington County Public Schools since the 1980s, Harrell said.