Fewer Fairfax County students took Advanced Placement tests in 2013 compared with the year before, according to data released by the school system this month. And among those students who did take the tests, scores declined slightly.

At the same time, the number of high-schoolers taking International Baccalaureate exams rose significantly compared with the previous year, as did performance on the exams.

This year, 16,233 Fairfax students — less than one percent fewer than the previous year — took 35,759 AP tests. Students need to score 3 or higher on the tests to receive a passing grade. The number of students who scored at least a 3 dropped two percentage points to 70 percent.

The number of students taking IB exams in 2013 totaled 3,154, an increase of 7.5 percent. Those students took 8,137 exams, with 6,037 — or 74 percent — of the exams receiving a 4 or better. That’s two percentage points higher than the previous year.

Overall, participation in AP and IB classes has been on an upswing since 2010. The number of AP tests taken has increased by five percent, while the number of IB exams taken has increased by 20 percent. Among black students, the number of those taking IB exams increased by 36 percent, and the number of Hispanic students taking IB tests increased by 54 percent.

School officials said 21 percent of all AP tests administered in the state were taken by Fairfax County students.

The number of AP tests taken by Asian students in the county increased by 20 percent since 2010, and Hispanic students had their participation increase by 53 percent.

From 2010 to 2013, the number of IB exams also saw similar increases among minority groups. The number of IB tests taken by black students increased by 29 percent while the number of tests administered to Hispanic students jumped by 81 percent. Scores for both ethnic groups also improved slightly.

The increase in the number of tests, however, did not lead to better scores overall for black or Hispanics, as the scores for both ethnic groups dropped slightly during that time.

Certain classes for both AP and IB saw increases in enrollment with participation in AP calculus BC increasing by 15.9 percent and AP biology increasing by 11.7 percent. In Fairfax, a total of 85 percent of students taking the AP calculus BC test scored a 3 or higher.

In IB, enrollment in IB chemistry increased by 14.4 percent, and enrollment in IB physics rose by 12.3 percent. At Marshall High School, 93 percent of all IB students qualified for the IB diploma, compared with 77 percent of all IB students across the county.

Most colleges and universities award credits to high school students who receive a 3 or higher out of 5 on AP tests and a 4 or higher out of 7 on IB exams.