Henri Poincare was a teacher.
Jules Henri Poincaré ( [ ʒyl ɑ̃ʁi pwɛ̃kaʁe ] ; 29 April 1854 -- 17 July 1912 ) was a French mathematician , theoretical physicist , engineer , and philosopher of science . A substitute teacher is a person who teaches a school class when the regular teacher is unavailable ; e.g. , because of illness , personal leave , or other reasons .