This paper presents the structural assessment of a portion of 'Giovanni Vinciguerra' School, located in the municipality of Anagni, Italy. In 2009, the presence of some cracks in the vaults of the basement led the authorities to close the building and declare it not usable. In this work, firstly a proper knowledge of the history, geometry and structural configuration of the school was achieved by means of bibliographic research, laser-scanner survey and visual inspections. During onsite inspections, the damage observed was also surveyed and mapped in detail. Then, structural analysis applying graphic statics and inverse piecewise rigid displacement (PRD) analysis was carried out with the aim to identify the causes of damage and evaluate the residual structural safety of the building. The results obtained allowed to prove that the structure is safe despite the occurrence of some damage in the basement.