In this photo taken Friday, December 9, 2016, young ballerinas practice under the instruction of Kenyan ballet dancer Joel Kioko, 16, in a room at a school in the Kibera slum of Nairobi, Kenya. (Photo by Ben Curtis/AP Photo)
A student from the General Yermolov Cadet School takes part in weapons training during a two-day field exercise near the village of Sengileyevskoye, just outside the south Russian city of Stavropol April 13, 2014. The General Yermolov Cadet School in the southern Russian city of Stavropol is a state-run institution that teaches military and patriotic classes in addition to a normal syllabus. (Photo by Eduard Korniyenko/Reuters)
Students at the Cuba's National Ballet School (ENB) watch a class from outside the classroom in Havana, Cuba, October 12, 2016. Catherine Conley, the first American full-time student at Cuba's prestigious National Ballet School, hopes to gain an edge back home by learning the powerful Cuban style with its dazzling turns and jumps. (Photo by Alexandre Meneghini/Reuters)
A Palestinian student jumps through a fire ring during a military-style show at a school in Rafah in the southern Gaza Strip March 28, 2016. (Photo by Ibraheem Abu Mustafa/Reuters)
School children dressed in traditional attire eat breakfast before participating in a Republic day parade in Bangalore, India, Thursday, January 26, 2017. (Photo by Aijaz Rahi/AP Photo)
Model Juliana Paesthe (C) of Viradouro samba school participates in the annual carnival parade in Rio de Janeiro's Sambadrome, February 15, 2015. (Photo by Ricardo Moraes/Reuters)
“The Challenge!” Young boy relishes in a game of tug of war before school. Photo location: Lake Titicaca, Peru. (Photo and caption by Paul Heyman/National Geographic Photo Contest)