Software Flexibility, Business Rules Technologies Flexibility is one of the most important characteristics of software systems for computerised school management and administration, in particular if the software has to be used in several institutions. Given that school institutions are diverse in many aspects and have their own specific needs, several problems are faced when developing unified software. In this paper we describe an approach to information system planning and development, which we believe can help to gain the required software flexibility. The main purpose of the paper is not to examine technical issues on information technologies but to emphasise the possibilities that have to be considered when developing software in support of management and administration in schools.