The problem of this research is how to use assessment for school learning and what are students' creative thinking skills? Research objectives: First, to uncover, analyze, identify, describe the learning assessment used by teachers and students of Nusantara Indah Sintang Senior High School. Second, to express, analyze and describe students' creative thinking skills. This study uses a descriptive qualitative research method of survey type. The population and sample are the teachers and students of Nusantara Indah Sintang Senior High School. Data collection tools in the form of questionnaires and interviews. Data analysis can be descriptive qualitative. The results of the study revealed that the use of assessment for learning in school was suboptimal or infrequent, both from teacher and student questionnaire data, as well as confirmed teacher and student interview data. Likewise, the creative thinking abilities of students who are also not optimally cheated or do it rarely can be seen from the teacher's questionnaire data - an average of 56.13 percent, while the students' questionnaire data, with an average of 1.66, do not agree with the category. In addition, it is confirmed by the interview data that the four indicators of creative thinking were not optimally enabled at school.