Correction: Earlier versions of this article incorrectly stated that the share of freshmen taking Algebra II has risen from about 65 percent five years ago to about 90 percent this year. In fact, those percentages indicate the share of freshmen who took either Algebra II or a higher level of math. This version has been corrected.

Educators at Fairfax County’s vaunted Thomas Jefferson High School for Science and Technology are seeking explanations for an unusual uptick in the number of freshmen who have struggled in math and science.

In recent years, about 8 percent of the school’s freshmen have landed on a “watch list” of students with grade-point averages below 3.3 on a 4-point scale. This year, that proportion nearly doubled, to 15 percent, and teachers said they were overwhelmed with students needing extra help.

Some teachers and administrators say the problem is that
middle-school kids are accelerating too quickly through high-level math classes. Others point to what they say is a flawed admissions process at the highly selective public school that serves a broad swath of Northern Virginia.

“We don’t know if this one year is an anomaly or if it’s an actual trend,” Evan Glazer, principal of the acclaimed school known as TJ, said Wednesday. “There are so many different possible root causes that we don’t have sufficient data at this point, in my opinion, to draw conclusions about where the problem may lie.”

The issue became public after seven TJ Algebra II teachers sent a letter dated April 16 to the School Board detailing their concerns. The letter, first reported May 17 by the Washington Examiner, said that too many students arrived at the school last fall ill equipped for its extraordinary academic demands.

Most of TJ’s approximately 480 freshmen take Algebra II, and every one of them passed the state end-of-course test this spring, according to school system officials. About 90 percent earned an advanced score.

But TJ’s famously fast-paced and intensive courses go far beyond the state-mandated curriculum. School policy says that students who fall below a B average, or 3.0, are in jeopardy of being returned to their neighborhood schools.

The watch-list spike caused officials to take a closer look at student performance. They identified an additional 15 percent of the Class of 2015 whose math and science grades indicated that while they were not yet in serious academic trouble, they were on the edge of it.

Both groups of students — 30 percent of freshmen — are getting extra support, Glazer said. The support varies, depending on need. Measures include study sessions with upperclassmen and small-group tutoring with teachers.

Why are students having trouble keeping up? In recent days, Fairfax has swirled with hypotheses.

Some have pointed out that more middle school students are racing through high school-level math courses, perhaps leaving them with gaps in basic skills.

At TJ, the proportion of freshmen taking Algebra II or a higher level of math — courses traditionally taken by juniors or advanced sophomores — jumped from about 65 percent five years ago to roughly 90 percent this year, Glazer said.

“Students, not just at TJ but all over the region, are accelerating in math at a very rapid rate,” said Glazer. “We’re starting to question, maybe we’ve accelerated too fast.”

The acceleration among TJ students mirrors a regional trend. A generation ago, most students were expected to take Algebra I in ninth grade. Now, many school systems aim for students to complete that course by eighth grade. More than two-thirds of Fairfax kids meet that goal.

“We have been collapsing the math curriculum for years now, with high school students doing college math, middle school kids doing high school math, and on down through the years in elementary school,” said Fairfax School Board member Pat Hynes (Hunter Mill).

Hynes said she had heard concern about that from all corners of the county. “We maybe need to put the brakes on a little bit,” she said, “and say we’re not giving kids enough time to get the foundations for math understanding.”

Others have said that ninth-graders’ trouble this year could be traced to the admissions process — which, critics say, overemphasizes written essays, underemphasizes teacher recommendations and features an exam that allows too many middling math students to squeak through.

“Exceptional math students are being rejected every year, and record numbers of students are struggling in math at TJ,” Grace Becker, president of the Fairfax County Association for the Gifted, wrote in an e-mail. “It’s unfortunate to see bright students who would otherwise be blossoming in base schools being put in an uncomfortable position at TJ.”

The teachers who wrote to the School Board studied TJ’s entrance exam and concluded that the math portion was written at a sixth-grade level, which they said was inappropriate for identifying the brightest eighth-graders.

Admissions officials said they have asked the company that created the test, Pearson, to address the criticism. The admissions process was last changed in 2009, so it’s not clear why significant problems did not arise until this school year.

“I believe it’s premature to single out the admissions policy as the root cause of the TJ teachers’ concerns,” said Tanisha Holland, the school’s admissions director. But, she added, “it is appropriate to examine the selection criteria to ensure that it is effective in identifying students for TJ.”

TJ’s admissions policy is the subject of perennial debate. It has been tweaked over the years in an effort to ensure that the student body, which is mostly white and Asian, better reflects the county’s racial and ethnic diversity. In July, the school board will consider whether the policy needs to be revised again.

Meanwhile, TJ officials said they will try to head off potential problems next school year by giving incoming freshmen a diagnostic exam. Those with gaps in knowledge will be invited to a summer “boot camp” to sharpen their skills.