Of York County's seven high schools, only those in Rock Hill saw their average score on the SAT college-readiness exam rise in 2010, according to results released Monday.
While Fort Mill's two high schools saw a slight dip in their average combined score in reading, writing and math, seniors at those campuses still performed among the state's top achievers - and well above the national average, which remained flat at 1,509.
The overall score for South Carolina's public and private schools fell for a second straight year. The state's average combined score dropped five points to 1,447.
Clover and York Comprehensive high schools each saw scores tumble. High schools in Chester and Lancaster counties posted mixed results.
The SAT, administered by the private College Board, is one of two widely-used annual exams designed to measure whether high school students are prepared for college. The other is the ACT.
The SAT tests students in math, writing and critical reading. Scores on each test range from 200 to 800. A perfect combined score is 2,400.
The College Board discourages using the scores to compare schools, because students choose whether to take the exam.
States and schools where smaller shares of students take the test tend to have higher averages, because a more select group of college-bound students are participating.
School leaders in York County say they encourage even marginal students to take the test, in hopes it will encourage them to apply for college.
"The most important thing is that students are prepared to take the SAT or the ACT," Fort Mill High Principal Dee Christopher said.
That includes not taking either too early.
For example, Christopher said, "If they haven't been through Algebra 2, they're not going to do well on the math portion."
Fort Mill High is one of several schools that saw a jump in participation - to 70 percent, up from 56 percent in 2009.
Northwestern, Rock Hill and Clover high schools also had a larger share of test-takers this year.
Across the state, school officials are struggling to determine the reason for score changes.
"The challenge is increasing test scores at the same time we increase test participation," Superintendent of Education Jim Rex said. "When you get a broader cross-section of kids, you typically get lower scores.
"We're seeing that with SAT scores but not with ACT and AP (advanced placement) scores, which keep improving even though more kids are taking the tests. We need to figure out how to expand our ACT and AP improvements to include SAT scores."
High schools should make better use of the preliminary SAT test, which students take earlier, to catch potential future problems, Rex said.
Local educators also are puzzled by changes.
Northwestern High posted the county's highest gain - 68 points. But the school hasn't been doing anything significantly different, the school's head guidance counselor Rena Hill said.
"We are doing exactly what we've always done," Hill said. "We are meeting with each student individually."
In those meetings, students and parents talk with a counselor about plans after high school. More parents seem to be participating, which Hill thinks might have contributed to the school's improved score.
Half of Northwestern's class of 2010 took the test.