A workshop for high school students on naive set theory
  In this article we present the prototype of a workshop on naive set theory designed for high school students in or around the seventh year of primary education. Our concept is based on two events which the author organized in 2006 and 2010 for students of elementary school and high school, respectively. The article also includes a practice report on the two workshops. 
Sven-Ake Wegner
math.HO