In 2005, the Brazilian Public Schools Math Olympics (OBMEP) was created by the Instituto de Matemática Pura e Aplicada. Since then, around 18 million students from the sixth to the twelfth grades have taken part in the competition annually. In each year of the competition, 6500 medals are distributed to public school students. In the following year these students receive a scholarship to participate in a training program disseminated in 225 centers across the country. Perceiving that the greatest impact of OBMEP has occurred in schools engaged with the Olympics, in either the preparation of their students for the competition or the promotion of award ceremonies for students classified as eligible for the second stage, in 2014 OBMEP launched a teacher training program. This article reviews the various OBMEP programs, their objectives and their impacts, and analyzes the obstacles faced. It also discusses the gender gap observed in the Math Olympics. In Brazil, the STEM areas of study, namely the sciences, technology, engineering, and mathematics, attract fewer girls than boys. A similar phenomenon can be observed at the OBMEP. The performance of girls is inferior to that of boys. This distinction is accentuated with the age of the students and in the grades of students in the upper percentiles of the exam.