Children leave a nearby school as a signs prohibiting the use of marijuana in a designated area is seen in Amsterdam, Wednesday Dec. 12, 2012. Amsterdams mayor Eeberhard van der Laan said Wednesday he would formally ban students from smoking marijuana at school as of Jan. 1, 2013, making the the Dutch capital the first city in the Netherlands to do so. Under the tolerance principle, marijuana is technically illegal here, but police cant prosecute people for possession of small amounts. Thats the loophole that made possible Amsterdams famed coffee shops _ cafes where marijuana is sold openly. But it has also had the unwanted side effect that Dutch children are frequently exposed to the drug in public areas. (AP Photo/Peter Dejong)