New Jersey- A sweet-faced New Jersey schoolgirl, described as a “gifted student,” was found dead in her underwear by the side of a road – and authorities believe she died of a drug overdose while secretly working as a $600-a-night hooker.

David Downey, a divorced financial executive in his 50s, told cops that he paid an escort service to have a “nice girl” delivered to his $500,000 home in well-to-do Limerick Township, Pa., on July 31.

Montgomery County prosecutors said in an affidavit that a stripper from the nearby Tattle Tail South club and her boyfriend dropped off 17-year-old Ashley Burg for a fee of $600, and that Downey gave her drugs.

The teen – with powder believed to be cocaine spread on her face – became ill and began running back and forth to the bathroom, clutching a trash can to vomit in, they said.

Later, she passed out and when Downey was unable to wake her, he called the escort service for help – but was told by a man who identified himself as Ashley’s boyfriend to “pick her up and throw her in the f – – – ing shower.”

He called again, demanded help and then agreed to pay $4,600 to get Ashley moved out of the house, according to the affidavit.

The pair from earlier, identified as Christy Shute and Mike Tees, dumped Ashley’s body, dressed only in black panties, near Interstate 95 on Aug. 1, police say.

It’s unclear whether she died at the house or after being carried out.

Montgomery County District Attorney Bruce Castor Jr. said Ashley’s tragic trip to Downey’s home may have been her first time as an escort.

“The working theory is that she might have fallen into drug use and things spiraled from there,” Castor told The Post.

Prosecutors said Downey had used the escort service about 15 times in the past four years. They said Shute had serviced him with oral sex, with a coked-up Downey telling her, “I’m your 12-year-old boy and you’re my 12-year-old little girl.”

Downey, a senior vice president at financial-consulting firm KSR Associates, has not yet been charged with any crime.

Friends said Ashley had left the mean streets of Philadelphia’s Fishtown section to live with an aunt in Willingboro, N.J., and make a better life for herself after realizing she was spending too much time with the wrong crowd.

She had turned into “a gifted student” at the Burlington County Institute of Technology, where she was about to enter her junior year.

“She was a great kid, your average 17-year-old,” her aunt, Tonya Sanderson, told the Courier-Post newspaper.

“It’s very shocking that’s all coming out. Things just don’t add up.”

“The family is very despondent. They felt like she had turned her life around,” said Philadelphia Homicide Lt. Phil Riehl.