I was a teacher of competitive programming for middle and high school students preparing for the Brazilian Olympiad in Informatics and the International Olympiad in Informatics at Organização Educacional Farias Brito.
I worked there from Nov 2016, after graduating from high school, until May 2017, before starting university. My classes to middle schoolers were mostly about programming logic and my classes to high schoolers involved advanced algorithms and data structures that are common in competitive programming.
Three of my students were able to classify to the International Olympiad in Informatics. Every year, four high school students from each associated country participate in this competition.