A middle school principal made a deal to buy $20 worth of crack cocaine in his office Thursday while students were still on campus, authorities said.

Anthony Giancola, 41, principal of Van Buren Middle School in Tampa, was arrested in the school lobby at 3:45 p.m. Thursday after buying drugs from an undercover police officer, Tampa police spokeswoman Laura McElroy said.

Giancola told the undercover officer last week he wanted to buy $200 worth of crack cocaine in his office at 7:30 p.m., McElroy said.

On Thursday, Giancola allegedly decided he wanted only $20 worth of crack and wanted to meet while school was still in session, McElroy said.

"It's a very disturbing case," McElroy said. "The officer expressed concern about doing the deal when school was in progress and (Giancola) said he could guarantee no students would be around and that was where he felt safe and secure."

Additional officers posed as parents in the school lobby while the deal took place. McElroy said they made sure no students were nearby.

Giancola, who lives in St. Petersburg, was charged with possession of cocaine and soliciting to purchase cocaine on school property, a felony that carries a minimum sentence of three years in prison, McElroy said. She said Giancola was cooperative with arresting officers.

"I'm very sorry," Giancola said Thursday as he was put in a patrol car in handcuffs.

It was not immediately clear if Giancola had an attorney.

Giancola has been a popular educator with the Hillsborough County school system since 1991, school district spokesman Steve Hegarty said. He worked as a special education teacher, an administrator and a principal at two schools. He took his most recent post last summer.

"This is completely out of the blue, a total shock," Hegarty said.

Giancola will be placed on paid administrative leave until school officials can investigate.

"He won't be coming around the school until we sort this out," Hegarty said.