Today in Pictures: Dec. 20, 2012

Students and a teacher try to stop an attacker during a drill on a mock attack at a primary school in Jinan, eastern China. The drill came days after a knife-wielding attacker stabbed 22 students at a primary school in the central Chinese province of Henan in the latest in a series of assaults. China has seen several violent attacks against children over the past two years. (AFP/Getty Images)