One of the major areas in Computer Aided Learning (CAL) research has been the development of Intelligent Tutoring Systems (ITSs) for tutoring individual subjects through the application of cognitive tutor technology. In parallel to the use of computer aided learning (CAL), Computer Based Testing (CBT) has also been widely used for a variety of purposes. Studies have shown that fractions are one of the most difficult subjects to learn due to the complexity of the concepts and skills involved. Although there are various fraction tutoring systems available, most of them lack user interactivity and do not provide intuitive insight into the many concepts and skills associated with fractions. Furthermore, these systems are generally intended for longer-term learning use (e.g. weeks or even longer) and the effectiveness of using such systems is therefore usually difficult to assess. This paper presents the development of an interactive computerised Fraction Testing and Tutoring System (FTTS) delivered through the World Wide Web that incorporates learning capabilities for the purpose of both tutoring and testing fractions for school students aged 10-12. The system implements the cognitive learning model proposed by Derry in 1990. This system can perform fraction tutoring and at the same time undertake fraction testing. Results obtained from the use of this system can therefore be used to assess the effect of tutoring on students’ performance.