This paper examines the role of collaborative working between special and mainstream schools and personnel as a vehicle to promote more inclusive practice within schools. The value of this approach has been observed during the course of development work, involving representatives from schools and Local Education Authorities (LEA) support services, within the context of a three year research project. This project was commissioned by the government SEN partnership for the East Midlands region (EMSEN), involving 10 LEAs and a UK University. The project brief reflected current government initiatives to promote effective recognition of attainment and progress for pupils with special educational needs (SEN) and collaborative working between LEAs, mainstream and special schools and personnel. The project aim was to support teachers in making judgments about pupil attainment, using national SEN performance scales (P Scales). The research project surveyed the current practice in schools across the East Midlands region of the UK (mainstream and special). In light of these findings, the project responded by developing training, materials and guidance to support the use of these national SEN performance scales across a range of educational settings. The final phase of the project is to cascade this training, offering flexible models of delivery to meet the diverse needs of schools and LEAs within this region of the UK. New government guidance and exemplar materials are pending and the project is endeavoring to substantiate these materials, by supporting schools in the process of using these performance scales. In addressing the identified needs of teachers in the region, it is envisaged that collaboration will promote a more inclusive assessment and moderation process, that values teacher assessment, shares expertise and practice and, gives confidence to practitioners in mainstream and special schools. Representatives from the region's schools and LEAs have been involved in the project development work, modeling some of the collaborative approaches examined in this paper. Benefits from these approaches were seen to be of a very reciprocal nature and led to fruitful exchange of expertise and sharing of practice within the context of special needs. It is suggested that establishing collaborative working practices, such as these, are likely to lead to a greater understanding of the needs of pupils with SEN and a more inclusive approach to the effective education of these pupils. The shared focus of an initiative, such as the SEN performance scales, it is suggested could provide an impetus for mainstream and special school personnel to work collaboratively on a larger scale. The very nature of a common approach by all schools to assess and monitor progress of all pupils in itself, we would suggest may promote more inclusive practice.