Students stick on the placard on National Narcotics Ban Awareness for All the Public, in the classroom of Yuhong Middle School, in north China's Tianjin Municipality, Nov. 19, 2008. Policemen on duty get on the campus to promote the knowledges and discretion of students on their understanding of the drugs ban, discerning the narcotics ban, and self-protection from drugs as well. [Xinhua]