Today's economy demands higher order thinking skills (HOTS), and the public education system has a critical role in supporting students' acquisition of HOTS. Yet, numerous studies documented inequity in access to higher quality instruction that promotes HOTS, which could result in wide test score gaps in HOTS. In this study, I examined test score gaps in HOTS and explored instructional practices associated with HOTS, particularly among low-performing students, using large-scale international assessment data from the 2015 Trends in Mathematics and Science Study. I found wide test score gaps in HOTS in mathematics between the lowest and highest socioeconomic status students and between White students and students of color. Instructional practices such as the same ability group work, asking students to work on problems with teacher guidance, and working on problems with no immediately obvious method of solution were found positively associated with the test scores.