Students with special educational needs (SEN) are systematically hindered in their participation in test-taking and, as a result, are also excluded from participating in high-quality learning. Hence, participation in the assessment situation is connected to power relations and future prospects and possibilities to participate in society. This article explores aspects of participation in a standardised and national assessment in Sweden by scrutinising a moment of mandatory national testing in mathematics with students in need of special education. The conclusions are that layers of access and levels of participation are established as the result of complex movements between communication, support, relations and the mathematics involved.