There is increasing evidence of a gap between curricular requirements and what students actually want to know. One of the factors influencing what is taught in the classroom is teachers' attitudes towards integrating their students' interests. This study investigated what prompts high-school teachers who prepare students for national matriculation examination to adjust the curriculum to match their students' interests. In the first stage of the study, 350 students' biology questions that are not covered by the Israeli biology curriculum were presented to 15 experienced biology teachers. These teachers provided 19 reasons why they would or would not address these questions in their teaching. In stage 2, these 19 reasons were presented to another 175 high-school teachers from different disciplines. These teachers were asked to rank the importance of each reason in deciding whether to include or exclude topics raised by the student which are not required by the curriculum. Based on these answers, the 19 reasons were classified into four groups: civic literacy, curricular compatibility, topic suitability, and curricular limitations. The findings show that demographic factors such as gender, experience, and sector, as well as the subject taught by the teacher, all influence decisions. Thus, many teachers are aware of the interest gap, but the solutions and the attention given to this problem vary.