**Abstract**

STEM education gives practice experiences for students. However, the assessment in identifying its impacts has not been developed in Indonesia widely. Teachers are responsible to assess students' achievements as an impact of learning activities. They said that they have difficulties in developing the assessment instruments. Therefore, workshop activity was designed to minimize and identified the difficulties. This study aims to evaluate teachers' experiences in developing assessments in STEM learning. Workshop activities were conducted over three days. It covered three main topics: the best practice of STEM education from experts, explanation of STEM literacy, and the group discussion session in creating STEM literacy assessment tools. The tools that were passed through the expert judgment process will be proceed to the validation process to find out its response from students. Data were analyzed using person separation method in Rasch model analysis. The result showed that the assessment tools are less sensitive in distinguishing students' abilities. It indicated that teachers should create more sensitive tools in diagnostic students' STEM literacy. It is also found that most of teachers face difficulties in creating technology and engineering literacy items.

**Keywords:** STEM literacy, teachers' difficulties, assessment, workshop, items validation
