Curiosity is an important driver of student's learning and school is a promising venue for promoting curiosity through social interactions between teachers and students. However, some research suggests that curiosity in school may decline with grade, perhaps due to educational practices (Engel, 2011). The current study assessed the frequency of curiosity promoting and suppressing instructional practices in 269 preschool math and science lessons across 72 classrooms/teachers (97% female, 80% White), exploring differences between subject and associations with student outcomes (N=456 students; 54.1 months, 49% female, 64% White). Consistent with prior research few instances of curiosity-promoting instruction were observed. Although the levels of promotion were similar between math and science, some differences in curiosity promotion were observed, with more variation in curiosity promotion between lessons than between teachers. Curiosity promotion was not associated with child math or science outcomes, but curiosity suppression was negatively associated with child task orientation. The current study demonstrates that it is possible to rigorously measure curiosity promotion in classrooms, and future work should examine strategies for encouraging curiosity promotion. [This paper was published in "Thinking Skills and Creativity" v49 Article 101333 2023.]