Computer-assisted assessment (CAA) has become increasingly important in education in recent years. A variety of computer software systems have been developed to help assess the performance of students at various levels. However, such systems are primarily designed to provide objective assessment of students and analysis of test items, and focus has been mainly placed on higher and further education. Although there are commercial professional systems available for use by primary and secondary educational institutions, such systems are generally expensive and require skilled expertise to operate. In view of the rapid progress made in the use of computer-based assessment for primary and secondary students by education authorities here in the UK and elsewhere, there is a need to develop systems which are economic and easy to use and can provide the necessary information that can help teachers improve students' performance. This paper presents the development of a software system that provides a range of functions including generating items and building item banks, designing tests, conducting tests on computers and analysing test results. Specifically, the system can generate information on the performance of students and test items that can be easily used to identify curriculum areas where students are under performing. A case study based on data collected from five secondary schools in Hong Kong involved in the Curriculum, Evaluation and Management Centre's Middle Years Information System Project, Durham University, UK, has been undertaken to demonstrate the use of the system for diagnostic and performance analysis. (PsycINFO Database Record (c) 2006 APA ) (journal abstract)