Prosecutors said Sandusky went on to sexually abuse other youths after Spanier failed to tell police about a report that Sandusky had molested a boy in a locker room shower in 2001.
Spanier's trial revolved around testimony by an ex-graduate coaching assistant, Mike McQueary, who said he reported seeing Sandusky molesting a boy in 2001.
At the center was Spanier, the 69-year-old who once ranked among the nation's longest-serving university leaders.
It has been a stunning downfall for Spanier, 68, who had spoken publicly about his own history of being abused as a child by his father, who beat him severely.
Spanier is still pursuing civil cases against both Louis Freeh, the former Federal Bureau of Investigation director who - in his initial report to trustees - gave gravitas to the theme of a Sandusky cover-up at Penn State; and his former employers.
Curley and Schultz also told the court they were sorry they didn't do more.
"I pleaded guilty because I felt like I should have done more", Curley said.
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"They ignored the opportunity to put an end to his crimes when they had a chance to do so", Judge John Boccabella said as he lambasted the three defendants and the Hall of Fame coach over a delay that prosecutors say enabled Sandusky to molest four more boys.
The defendants are "good people who made a awful mistake", the judge said. "Why no one made a phone call to police ... is beyond me", he said. Paterno was sacked but never charged with a crime; he died of lung cancer at age 85 two months after Sandusky's arrest.
The university has paid tens of millions of dollars to settle lawsuits filed by Sandusky's victims, and the total could eventually exceed $100 million. Spanier was also a fascinating character: He studied sociology and wrote papers about mate-swapping and extramarital behavior, which made for entertaining reading for students.
In addition, Schultz, the former university vice president, could serve a minimum of two months in jail and a maximum of 23 months; and Curley, the former university athletic director, could serve a minimum of three months in jail and maximum of 23 months.
The Penn State Jerry Sandusky child sex abuse case destroyed so many young lives. Sentencing guidelines call for up to a year in prison. The sentence for the misdemeanor offense will be four to 12 months incarceration, two years of probation and a $7,500 fine. Former athletic director Gary Schultz was sentenced to six to 23 months' confinement, with at least two months in jail, and fined $5,000. The emails the men exchanged in 2001 as Curley suggested changing the plan and Spanier agreed formed the core of the prosecution's case.
Silver recommended probation and community service, noting that more than 200 letters from college presidents, deans, professors, clergy members and others were submitted in support of Spanier.
Spanier and his lawyer, Sam Silver, declined to comment as they left the courthouse.
Spanier said he regretted that I did not intervene more forcefully. Schultz said: It really sickens me to think I might have played a part in children being hurt..