This paper outlines a toolkit designed to evaluate the natural science skills of 3rd grade students. This work is part of a broader initiative to create a flexible measurement system for evaluating STEM skills across students in grades 1 through 10. The aim of this paper is to detail the tools employed, showcase the findings from the initial testing, and discuss the gathered data. A total of 850 students from primary, secondary, and vocational schools in small to medium-sized towns across Bulgaria participated in the research. Three distinct methods were utilized to assess the students' scientific knowledge and key skills.

The initial method involved a survey with questions aligned with the 3rd grade curriculum, encouraging students to use reasoning and apply their knowledge to describe practical scenarios rather than just reciting facts. This approach aimed to evaluate the students' STEM skills and their capacity to apply knowledge in various domains.

The second method used was the brainstorming approach, where students worked in small groups (3-5 members) to create a word cloud related to a specific scientific topic within a designated time. This method assessed not only the students' scientific understanding but also essential skills like teamwork, tolerance, and effective communication.

The third method involved focus groups where students developed a series of arguments to justify the importance of understanding certain scientific topics and how such knowledge applies to real-world scenarios.

Together, these methods form a comprehensive system under development for assessing STEM skills in elementary and middle school students.

Keywords: STEM competencies, adaptive assessment metric, natural science competencies, primary and secondary school.