This paper proposes a multidimensional index that summarizes three relevant aspects of the educational achievements, out of the data provided by the PISA Report, concerning reading abilities of 15-year-old students from 65 countries. The three aspects considered are: performance, equity, and quality. The Educational Development Index (EDI) is the geometric mean of the normalized values of those three variables. We analyse the distribution of the variables that approach those three aspects and the resulting index, relative to the corresponding means of the OECD countries.