Investigators looking into an SAT cheating scandal in Nassau County believe there was a "market" that paid impostor test-takers on a sliding scale for delivering high scores, a source close to the probe said Tuesday.

At least two test-takers, including Sam Eshaghoff, who was arrested last month for impersonating students and taking the exam, were operating out of Great Neck North High School since the 2008-09 school year, according to two sources with knowledge of the investigation.

Eshaghoff, 19, of Great Neck, whose scores ranked in the top 5 percent of all test-takers and who was paid up to $2,500 per test, would have been at the upper end of the pay scale, a source said.

District Attorney Kathleen Rice said she expects more arrests in the probe that has expanded to include two school districts outside of Great Neck North and one private school. The schools being investigated have not been identified.

She has also subpoenaed documents from ETS, the nonprofit agency that administers the college entrance examination, spokesman John Byrne said.

Because college and university admissions have become increasingly competitive, high SAT scores -- perfect is 2400 -- are sought after. The lowest score Eshaghoff got for his clients was 2140 and the highest was 2220, substantially higher than last year's average nationwide score of 1509.

advertisement | advertise on newsday

"Investigators have also identified additional students who paid someone else to take the test for them. School administrators are cooperating," Rice said.

Eshaghoff, who graduated from Great Neck North in 2010 and now attends Emory University, pleaded not guilty to criminal impersonation and other charges and is free on bail. He was scheduled to appear for a conference in Nassau County Court in Mineola Tuesday, but the case was adjourned. Eshaghoff faces four years in prison if found guilty.

Six former or current Great Neck North students who were arrested on misdemeanor charges that they hired Eshaghoff to assume their identifies and take the test for them, have been released. They were younger than 19 when the phony testing took place and prosecutors did not identify them.

Eshaghoff's lawyer, Matin Emouna of Mineola, said he's gotten calls from across the country since the story broke.

"I believe this is a nationwide epidemic," he said. "To say it's not is like saying drugs don't exist in schools."

An ETS spokesman, Tom Ewing, said the company hadn't received the subpoena yet, but "welcomed the opportunity to provide any additional information" to Rice.

Authorities have said they began looking at other Nassau County schools after receiving a tip during the Great Neck North cheating probe. They have focused on students who took the exam at other schools and whose grade-point averages are less impressive than their test scores.

Prosecutors have said the colleges probably don't know the students cheated. ETS does not notify colleges or high schools when students are suspected of cheating. Instead, ETS cancels their scores and offers them a refund, a free retest or the opportunity to arbitrate, prosecutors said.