Context: Baseline testing for concussive injuries has been recommended by several expert panels and medical organizations. In many settings, these tests are administered at the beginning of an athlete’s academic career. It is unknown if a single test administration can provide the reliability necessary for clinical interpretation beyond the current playing season. Objective: To establish if a single neurocognitive assessment is sufficient for concussion management across an academic career. Design: Repeated measures. Setting: High school computer laboratory. Participants: Interscholastic football athletes [N=31, 16.4(+0.5) years, height 181.0(+6.0) cm, mass 88.9(+18.1)kg, 10.1(+0.5) years of education, and 0.5(+0.8) previously diagnosed concussions]. Interventions: Each athlete twice completed the ImPACT neurocognitive assessment for concussion on an annual basis prior to the competitive season. Testing sessions were separated by 353.2(+87.3) days. Main Outcome Measures: ImPACT scores (verbal memory, visual memory, visual motor speed reaction time, impulse control, and total symptom reports were evaluated using intraclass correlations (ICC 2,1). Reliable change indices were applied to output scores to identify athletes with notable performance changes between sessions. Results: Reliability (ICC: 95% confidence interval) for the ImPACT output scores were calculated at: verbal memory (.38: .04 to .64), visual memory (.29: -.07 to .58), visual motor speed (.49: .16 to .71), reaction time (.23: -.13 to .54), impulse control (.39: .05 to .65), and total symptoms (.46: .13 to .70). Notable performance changes were noted in 71% of the sample with 45% showing a performance decline and while 55% of the athletes improved over time. Conclusions: The athletes in this sample demonstrated variable performance across the two testing sessions. Not all athletes demonstrated change on all variables, but the results suggest that a single neurocognitive baseline measure may not be sufficient for an athletes playing career. Annual or multiple baseline assessments should be considered.