This paper analyzes an innovative experience of formative assessment aimed at improving the teaching of Statistics, which could be easily extrapolated to other studies. We detail the implementation of the double correction, consisting of correcting students' work twice. With the first correction, carried out by classmates according to a rubric developed by the academic, possible errors or deficiencies are discovered, and students are provided with a feedback that allows them to correct and improve their work before being graded by the teacher; whereas in the second correction of the work, once upgraded, the professor evaluates and grades the work. As a result, there is a significant improvement in the quality of students" works, and an active learning from their own mistakes. Both contents and competencies are reinforced by the experience.