The role of schools in democratic education is essential to build more equitable and inclusive societies. The literature highlights the lack of instruments for evaluating support strategies in this field with adequate psychometric properties. The aim of this work was to create the questionnaire “Coexistence and democratic participation in schools” based on validation by expert judges and reliability analysis through a pilot study. Sixteen experts in the subject and methodological aspects participated as judges, and 136 school principals participated in the pilot study. A content validity analysis and a reliability study of the instrument were carried out. The results indicate an adequate content validity and an acceptable reliability, with a correlation level between.6 and.7 for most of the items and acceptable reliability, with a Cronbach’s alpha value of.876 for the Coexistence dimension, and a Cronbach’s alpha value of.886 for the Participation dimension. From the judges’ evaluations and the pilot test, it became clear that the behavior of some items needed to be revised based on the correlations of each item with its subscale.