Twenty years ago, the European School of Madrid began to implement P4C. Félix García Moriyón trained a group of teachers through an intensive workshop and Elena Morilla coordinated the whole process thereafter. P4C was integrated within the regular curriculum and students attended one class per week since primary school to the end of high-school. After obtaining informed consent from both the school staff and the students' families, a longitudinal study began in 2002 for investigating the presumed lasting positive impact of (...) P4C over cognitive and non-cognitive factors, and also over academic achievement. To the best of our knowledge this research is unique because there is only one long-term study and the remaining research was made in the short-term. So far we have been following more than 400 students in the treatment group and more than 300 students in a control group. As required, both groups shared closely similar social and cultural backgrounds: both are private schools in a small village, mainly residential, 18 km and 32 km away from Madrid, same highway A-6, etc. Students came from middle-upper class families, and middle-upper social and cultural status. We recruited six cohorts from the P4C school and five cohorts from the control school across the years. Data were collected at three time points: 2nd grade, 6th grade, and 4th grade of secondary school. The administered measures tapped cognitive abilities, basic personality traits, and academic achievement. This research tests the hypothesis that "IF P4C improves cognitive and non-cognitive basic psychological traits, THEN the treatment group will show greater scores in the standardized measures of both psychological factors". Here we present a summary of the evidence accumulated in the past 10 years. These were the main results: P4C promotes an average advantage of half a standard deviation in general cognitive ability, the average advantage is especially noteworthy in the lowest tail of the cognitive distribution across the years, lower percentages of participants in the training group can be found at the risk area, and P4C children are more prone to pro-social behavior, but they are also a bit more emotionally unstable. (shrink)