This research was carried out to determine the effectiveness and functionality of the word association test (WAT), which is a formative assessment tool that is frequently emphasized on today's modern education systems. The study group consisted of 60 students in a public school in Kocaeli in the school year 2018-2019. Participants were identified using convenience sampling technique. The data of the study were obtained by using pre-test and post-test quasi-experimental design with no control group. The data were categorized by subjecting to content analysis. The findings were tabulated using the cut-off technique and analyzed using the Wilcoxon signed-rank test. When the results of the study were examined, it was concluded that conceptual change and development occurred in participants' minds and there was a significant difference in the results of the Wilcoxon test performed before and after the implementation. It was observed that the students wrote 1669 words before the implementation, and the number increased to 2193 after it. This shows that the students associate the key concept of "migration" with more words after the implementation and thus there is a wider connotation related to migration in their minds. In addition, the results of this research reveal that the WAT is suitable for formative assessment and can be used in educational studies.