These 6 men revolutionized teaching. Every teacher should be aware of their works and how they apply to the classroom. Especially considering the fact that between the 6 of them, their theories are central to modern teaching.
Finland spends 30 percent less per student than the United States, yet 96 percent of Finns graduate high school and 66 percent go to college. 26 amazing facts about Finland's school system: http://www.businessinsider.com/finland-education-school-2011-12?op=1