This study was guided by the question, how do we understand the multiplicative reasoning of upper high school students and use that to give insight to their performance on a standardized test? After administering a partial ACT assessment to a class of high school students, we identified students to make comparisons between low and high scoring students on the sample assessment. Through a written assessment targeted towards assessing students' number sequences, and through semi-structured interviews with two students, we documented a direct relationship between a student's number sequence and their performance on the partial assessment. The evidence that students showed of limited multiplicative reasoning skills help explain some of their challenges in responding to prompts on the ACT assessment. This study reflects the need to give more focused attention to the multiplicative reasoning skills of secondary students and to design interventions that might develop these students' multiplicative reasoning and number sequences.