In past decades, schools have installed metal detectors, hired extra security to patrol grounds and hallways and instituted other zero-tolerance measures to make campuses safer.

CNN: How to deal with guns in school

Its mayor is Ray Mallon, a controversial police chief turned local official who showed an early interest in zero-tolerance measures and was elected as an independent.

ECONOMIST: Reshaping local government

As Greek society experiences unparalleled social, political and economic crises, it is still uncertain what peoples' tolerance levels will be once further austerity measures -- and their consequences -- are implemented.

CNN: Greece: When anger goes beyond despair

But a report released by a zero-tolerance task force assembled and published by the American Psychological Association in 2008 concluded there was no evidence that these measures were effective in making students and staff feel safer.

CNN: How to deal with guns in school

When used in conjunction with other measures, the Sharpe ratio can help investors develop a strategy that matches both their return needs and risk tolerance, advisers say.

WSJ: What Is a Sharpe Ratio?