This study aims to understand middle and high school students' ecosystem knowledge including knowledge about the food web, food pyramid, and energy flow. The data were collected from 250 middle school and high school students. Students' drawings were used to collect data and coded as correct, wrong, or no answer. Then, students' wrong answers were re-analysed to reveal common problems students had in the ecosystem topic. Findings showed that participants were mainly unsuccessful in their drawings. Only 2% of them could correctly draw food webs, and 10% of the participants could draw food pyramids correctly. Among 250 students, only one student could successfully draw energy flow. Moreover, various problems were identified in students' drawings. For example, 94% of middle school students could not show fungi as decomposers in their food web drawing. Similarly, more than half of all students (67%) placed living organisms in the wrong trophic level when they drew a food pyramid. Likewise, only five high school students used the sun as the starting point of energy flow. Considering the findings, students' ecosystem knowledge is discussed and implications are presented.