The objective of this study was to describe the content validation, through expert judgment, of a questionnaire for determining the level of knowledge that school teachers have of diabetes in order to design relevant educational interventions to improve the health of school-aged children. This psychometric study involved 15 experts who assessed each of the items in the instrument. The results revealed that the strength of agreement shown by the questionnaire ranged from substantial to almost perfect in its four dimensions, with the characteristics of "sufficiency" and "relevance" having the highest scores (0.982 and 0.903, respectively) based on the judgments made by the participating experts. Regarding statistical significance, the characteristics "sufficiency", with p < 0.001, and "relevance", with p = 0.001, were particularly relevant. The overall degree of understandability for the new version of the instrument was high (91.54%). The psychometric results obtained from validation of the "grado de conocimientos sobre diabetes en docentes del ámbito escolar" (Spanish for "level of knowledge of diabetes in school teachers")-GCDDaE questionnaire through expert judgment and the pre-test indicate that it is recommended for use as it is both relevant and quick and easy to administer.
Keywords: Fleiss’ κ; content validity; expert judgment; questionnaire; schools; type 1 diabetes.