Reilly also sexually touched a 17th student in June 2007, according to charges in a grand jury indictment made public Wednesday.
"Our thoughts and prayers go out to the victims and their families, and may justice take its course on this sad matter," Borough Mayor Christopher Green said. He called the charges "disturbing."
Victims ranged from ages 12 to 16 at the time, authorities said.
Reilly was single and had no children, former Mayor Fred Costantino said when Reilly was first charged in March 2011.
Reilly was then represented by Haddonfield lawyer Robert N. Agre. Agre could not be reached Wednesday and an office representative could not immediately say if he still represented Reilly. A phone call to Reilly's Pine Hill home was not returned.
Reilly was nearing the end of his second three-year council term when he was charged with endangering the welfare of a student who told his parents of explicit conversations, which sparked an investigation.
Days later, nine more victims came forward, and he was accused of having similar conversations with them.
Around that time, Reilly also had explicit Facebook chats with an undercover officer posing as an adolescent boy, official said.
Reilly, who was active in the American Legion, resigned from the council shortly after the initial charges, Green said.
The Jan. 23 indictment - which resulted from evidence presented by the 17 males - includes one count of second-degree sexual assault and 18 counts each of endangering the welfare of a child and official misconduct.
Reilly was also indicted on 42 counts of endangering the welfare of a child after child pornography was found on his computer at his home. The images were not of any children Reilly knew and were likely downloaded from the Internet, said Jason Laughlin, the prosecutor's spokesman.
Reilly, who was suspended with pay in March 2011, was suspended without pay Wednesday, district superintendent Kenneth P. Koczur said. Koczur said Reilly, who has taught at the middle school since 2001, also coached track and soccer at Overbrook High School.
"I was shocked at that time of the charges," Green said. "I'm even more shocked today."
Contact Darran Simon at 856-779-3829 or at email@example.com, or follow on Twitter @darransimon.