Formative assessment is a teaching method that helps to determine the prior knowledge of students, schedule the course plan accordingly, give it the final shape based on the feedback received from students, and encourage conceptual learning. The aim of this study is to introduce the "annotated student drawings" as one of the common formative assessment strategies used in science courses in middle schools and to evaluate the practices. The study was conducted during the classes of two science teachers who are doing their master's degree. In total, 48 students participated in the study from 5th (20) and 6th (28) grades. For data collection tools, annotated student drawings on the concepts of "pollination" and "water cycle" before and after the intervention and the science teachers' feedback about the strategy were used. The pre and post-interventional annotated drawings of the middle school students were compared. On both concepts, it was several alternative conceptions from the students' pre-interventional annotated drawings that were recovered on the post-interventional drawings. The findings indicated that the annotated student drawings are fairly effective formative assessment strategies in uncovering the prior knowledge and alternative conceptions of students in class. After the intervention, the students' second drawings gave detailed information on how the students' level of understandings improved. Formative assessment techniques are suggested to be used by science teachers instead of traditional assessments in order to: 1) Getting info about their students' initial understanding; 2) Reshaping their classroom instruction according to the feedback they get from their students; and 3) Always revising their interventional methods until the students got the main idea during the teaching period.