Teacher Guillermo Valenzuela poses for a picture with students of primary grade who are attending a night school for adults at Laura Vicuna school, in a popular neighbourhood of Santiago, September 10, 2015. Nearly three years after Taliban gunmen shot Pakistani schoolgirl Malala Yousafzai, the teenage activist last week urged world leaders gathered in New York to help millions more children go to school. World Teachers' Day falls on 5 October, a Unesco initiative highlighting the work of educators struggling to teach children amid intimidation in Pakistan, conflict in Syria or poverty in Vietnam. Even so, there have been some improvements: the number of children not attending primary school has plummeted to an estimated 57 million worldwide in 2015, the U.N. says, down from 100 million 15 years ago. Reuters photographers have documented learning around the world, from well-resourced schools to pupils crammed into corridors in the Philippines, on boats in Brazil or in crowded classrooms in Burundi. REUTERS/Ivan AlvaradoPICTURE 7 OF 47 FOR WIDER IMAGE STORY "SCHOOLS AROUND THE WORLD"SEARCH "EDUCATORS SCHOOLS" FOR ALL IMAGES