Purpose: Our US medical school uses National Board of Medical Examiners (NBME) tests as progress tests during the pre-clerkship curriculum to assess students. In this study, we examined students' growth patterns using progress tests in the first year of medical school to identify students at risk for failing United States Medical Licensing Examination (USMLE) Step 1. Method: Growth Mixture Modeling (GMM) was used to examine the growth trajectories based on NBME progress test scores in the first year of medical school. Achieving a passing score on the USMLE Step 1 at the end of the second year of medical school was used as the distal outcome, controlling for Medical College Admissions Test (MCAT) scores and underrepresented in medicine (URiM) status. Results: A total of 518 students from a US medical school were included in the analysis. Five different growth patterns were identified based on students' NBME test results. Seventy-eight students identified in Group 1 had the lowest starting NBME test score (mean = 33.6, 95% CI 32.0-35.2) and lowest growth rate (mean = 2.30, 95% CI 2.06-2.53). All 26 students who failed Step 1 at the end of the second year were in Group 1 (failing rate = 33%). Meanwhile Group 4 (n = 65 students) had moderate starting NBME test scores (mean = 37.9, 95% CI 36.3-39.0) but the highest growth rate with mean slope at 6.07 (95% CI 5.40-6.73). This group of students achieved significant higher USMLE Step1 scores comparing with the 3 other groups of students (P < 0.05). Conclusions: Our study found students had heterogeneous growth patterns in progress test results in their first year of medical school. Growth patterns were highly predictive of USMLE step 1 results. This study can provide performance benchmarks for our future students to assess their progress and for medical educators to identify students who need support and guidance.