The Positive Behaviour Intervention and Support system is a framework aimed to introduce a change at school-wide level. It promotes a disciplinary system change process, from a reactive punishmentbased strategies of specific student misbehaviours to a proactive system, where different behavioural principles such as the modelling and reinforcement of positive prosocial students' behaviours are applied to improve school values and to create a positive climate. This paper presents the Behavioural Assessment to improve School Environment (BASE) system and the BASE repository. The BASE system supports evidence-based digital intervention practices for stimulating the academic, social, emotional, and behavioural competencies of all students. The BASE repository is a collection of good practices, tools, and instructional contents. Both of the tools are able to support and facilitate, through the use of mobile devices and a web-based responsive system, different prevention and instructional practices at the three-tiers PBS model. At the first level of prevention (Tier 1) the system allows to the school PBS team to define the Expectation Matrix, a set of positive behaviours grouped according to predefined school values and locations. Moreover, the PBS team members are able to define the list of problem behaviours, classifying them in minor and major. The matrix and the list of minor and major problem behaviours are at the base of the development of a screening tool for identifying behavioural risk problems, the Positive Office Referral and the Office Disciplinary Referral tools. At the target prevention level (Tier 2) the BASE application provides the Check-in/Check-out (CICO) tool, as PBIS recommends. It is addressed to a targeted group of students, resulted unresponsive to the Tier I, and implements the practice of 'Positive reinforcement contingent on meeting behavioural goals' throughout a reward system. At the intensive prevention level (Tier 3) the system allows users to perform Functional Behaviour Assessment for students considered unresponsive to Tier I and II and to create customized measurement tools for designing single case studies. The measure can be assigned to the observers able to collect data and organize them in phases. A TAU analysis algorithm is applied to the gathered data for showing the effectiveness of intervention. In the BASE application, each student can access to the system with personal credentials and to visualize his significant progresses into a smart dashboard. The BASE repository represents a hub for digital resources collection concerning both theoretical and methodological aspects of the PBIS approach. The Internet users interested to know the European experience of the involved partner schools, and to enlarge their knowledge about the principles to implement the PBIS in their own school, can find a first set of multimedia contents, webinars, collection of good practices gathered during the lifespan of the European Erasmus+ BASE project. The repository facilitates the finding of high-qu...