The purpose of the study is to investigate the formative assessment work in Swedish compulsory special school, for students who read focus subject. The questions are how special educators working with formative assessment in different ways, and how they make the knowledge requirements visible by artefacts as the use of image support, alternative communication, digital tools and more. Theoretical approach consists of previous research on formative assessment. Sociocultural perspective has been used to analyse the results. Qualitative methods in the form of five observations and five interviews were used for the collection of empirical data. Results show that educators are working consistently with formative assessment in different ways and that teacher’s give students feedback for learning forward. In the categories peer assessment and the visibility of the knowledge requirements, it appears on the basis that it appears less in teaching. The study's implications based on the results is to make visible the objectives for students and help them to their own development. It also contributes to further research on the importance of students with intellectual disabilities may need alternative individual adaptations for perceiving information and communication about learning objectives and criteria. The work of visible learning and make students involved in their own development becomes more complicated when the curriculum and syllabuses exist only as text documents. Teachers need to create own image support in the student's immediate environment to increase the possibility for communication about the student's knowledge of the formative process