Eighty-one students from Washington area high schools, including 10 Landon School seniors who admitted cheating, were notified yesterday that their scores on the SAT given Oct. 12 have been thrown out because of "testing irregularities."

In a letter sent to the students yesterday, investigators for the Educational Testing Service said that the way the college-entrance exam was administered in two rooms at Holton-Arms, a private girls' school in Bethesda, was so improper that ETS could not stand behind any student's score.

The action leaves some students scrambling to meet college application requirements and scholarship deadlines; others worried that their reputations are tainted.

"These were the best scores I had gotten. I was really proud with how I'd done. And now it doesn't count," said Sarah Pulaski, an 18-year-old senior at Holton-Arms, who on that sunny Saturday took the SAT for the third time in her high school career.

"I definitely had nothing to do with the cheating," she said. "I didn't do anything wrong, and I'm being penalized. Now I'm worried that colleges are going to think I don't have integrity."

Pulaski and the other students will be allowed to retake the SAT on Jan. 11, or a later date, and their scores will be sent to colleges as substitutes for the rescinded results. Students also can choose to not retake the exam and receive a refund. In those cases, a letter will be sent to colleges next month to inform them that the Oct. 12 scores are invalid, ETS officials said.

The investigation was sparked by rumors that some seniors at Landon, a private boys' school in Bethesda, sat together in the Holton-Arms library that day and cheated. Eight Landon seniors were suspended in late November after they owned up. Two others were given the chance to withdraw -- before being expelled -- because they admitted cheating only after they were confronted.

The ETS letter, sent yesterday, made no mention of the incident. Investigators outlined the irregularities they found: Students were allowed to choose their own seats in the Holton-Arms library, including at study carrels that obstructed the view of test proctors -- violations of ETS guidelines.

In another of the school's testing areas, Room 311, SAT instructions were not read verbatim, as ETS requires, and the strict time limits on each exam section were not followed. Investigators said the proctor also allegedly left that room unattended for a time.

Also, the letter said, "ETS received statements from test-takers advising that copying/communication occurred" in Room 311.

ETS investigators visited Holton-Arms, interviewed students and staff who were in each of the seven testing rooms, and compared test answers and scores. "We found multiple standards not being adhered to in both rooms," said Ray Nicosia, the testing services' director of security. "Students should have been watched more closely in the library."

Nicosia said such a large-scale score cancellation, though not unheard of, is rare.

Brittany Greenfield, 17, a Holton-Arms senior, said she was in the library that day, also taking the SAT for the third time. Like others there, she had taken SAT prep courses and was acutely aware of how critical high scores are for getting into top-notch colleges.

Like several others, her October scores were her best.

"They were so selfish," she said of the Landon students who have admitted cheating. "They were affecting not just their own lives but every single person in that testing center."

Letitia Peterson, director of college counseling at Holton-Arms, plans to write a letter to each college that students such as Pulaski and Greenfield have applied to for admission. "I want to let [the colleges] know there was no impropriety in their behavior," she said, "and that they had to suffer because of the circumstances."

Diana Beebe, headmistress of Holton-Arms, called the score cancellations and the cheating incident devastating. "We've been a testing center for 25 years," she said, "and we've never had a peep of a problem."

As a result of the investigation, students will no longer be allowed to take the SAT in the Holton-Arms library, she said, and the proctor in charge of Room 311 will not be used again.

Part of the problem, Beebe said, was that the morning of Oct. 12 was chaotic. Students began arriving at Holton-Arms about 8 a.m., jittery and afraid. An 11th sniper victim had been shot the day before. Several proctors thought the test would be called off because of the sniper crisis. Some showed up as much as an hour late.

Greenfield said that as students chose seats in the library, she became suspicious when one Landon student waved his friends over to a group of study carrels in the back and called out loudly, "Hey guys, this is perfect."

Unlike the cluster of study carrels in the center of the library -- beneath an enormous skylight and with sunlight glancing in from floor-to-ceiling windows -- those study carrels are nestled under a balcony and hidden from view by a long shelf of reference books.

Whether premeditated or an act of opportunity, what happened next was nudging, whispering and sharing answers, said parents of some students involved.

About a month later, on Nov. 16, eight Landon seniors waited with their parents at 8 a.m. outside Headmaster Damon F. Bradley's office. One by one, they confessed that they had cheated. The following Friday, Bradley confronted two others, who then admitted cheating as well.

After honor council hearings, Bradley suspended the eight for the remainder of the first semester and recommended expulsion for the other two, who have since enrolled in other schools.