Invoice from Scholastic School Supply. Authorities say the company was fake and accuse Robert Armstrong of operating a scam that defrauded thousands of schools. (CBS) Invoice from Scholastic School Supply. Authorities say the company was fake and accuse Robert Armstrong of operating a scam that defrauded thousands of schools. (CBS)

SAN FRANCISCO (KPIX 5) – Bay Area schools have been put on notice about a potential scam that could cost them. Investigators believe the man behind the scheme allegedly defrauded thousands of schools across the country in a fake billing scam.

When a CBS News crew caught up to Robert Armstrong at his home in New Jersey, he was a man of few words.

While not vocal, investigators said Armstrong was very active. The case against Armstrong contends he was sending out tens of thousands of bogus invoices to schools all across the country, including the Bay Area.

Armstrong eventually agreed to talk. “Invoices were sent. Some on my behalf. Some were not authorized. And that’s pretty much all that I can say,” he said.

The criminal complaint filed against Armstrong outlines where he mailed out 70,000 false invoices from a fake company called Scholastic School Supply. An untold number of schools paid the bills, thinking they were legitimate. The typical bill was $647.50, and payments went to drop boxes in Las Vegas and New Jersey.

“It really looked legit,” said Elsa Roberts, the account clerk at Terra Nova High School in Pacifica. Roberts received one of the bogus invoices in September.

It was supposedly due in 30 days, but with a helpful way to pay.

“Because he even was so kind to give me an envelope to send it to that was already pre-addressed,” Roberts told KPIX 5.

The more she started investigating the mysterious math workbook the school was billed for, numbers just didn’t add up.

“I asked the teachers, nobody was able to tell me anything about it and neither was the library. I asked the principal and she said, ‘Well I didn’t order it. And if they didn’t either, let’s call those numbers that are on there, let’s contact them,’” Roberts recalled.

The phone numbers were fake too. So Roberts went online and, as it turned out, joined hundreds of others schools in filing a complaint.

Court documents also mention a “victim school” in San Francisco. The public school district declined our request for an interview, but did tell KPIX 5 they sent out an alert about the fake invoices, and none of them got paid.

Armstrong is charged with mail fraud, because he allegedly used the U.S. Postal Service to send the bills and receive payments.

Postal inspector Jeffrey Fitch said casting a wide net and billing for acceptable amounts are typical in fraud cases.

“They may understand what your minimum amount is that you need a signature from a supervisor,” Fitch said. “And they may say to you on the bill that you’re late. They’re doing what they can to make you think that you have to pay it.”

Roberts points out, no school can afford to lose money.