The present article shows the connection between sex education workshops and mathematics teaching, and how schoolchildren can learn from this discipline more healthy and caring behaviors regarding their sexual life. The schoolchildren who have received sex education in the math context recall more about sexually transmitted diseases (STDs) and claim to be better acquainted with prevention methods. A significant advance of our sexual and reproductive health program is the sharp decrease of 15% (p < 0.025) among adolescents who never use condoms. Thus, the teaching of mathematics adequately oriented to sex education may contribute (along with other school disciplines) to greater protection of adolescents, in the southern region of Brazil. Also, it is possible to confirm that creative educational strategies can make a big difference in the prevention of adolescents and young people contamination with STDs, in Brazil and worldwide.