Objective: While research on concussion/MTBI is relatively new, most done within the last 10 years, research on the effect of concussion/MTBI with individuals younger than high school age is very rare. With the introduction of ImPACT (Immediate Post-concussion Assessment and Cognitive Testing), a computer-based neuropsychological evaluation, effects of concussion/MTBI can now easily be compared to baseline cognitive functioning. Method: ImPACT was normed on individuals 15 years and older, negating its usefulness to younger children. My study not only involves norming ImPACT on ages 11–14, but shows the important differences between early adolescents and older individuals. Two hundred subjects, balanced for age and sex, will be given ImPACT, and their Index scores will be calculated. Results: The results show that there is a significant difference between young adolescents and older individuals in terms of the norms on ImPACT scales such as memory, reaction time, and speed of processing. There is less of a difference in terms of sex, and individual ages within that range. Conclusions: When using computer-based instruments to measure cognitive functioning after concussion/MTBI, age and developmental levels need to be taken into account in evaluating if there is any injury, the severity of the injury, and the rate of recovery. Due to their developing brain, these results are significantly different for young adolescents as compared to older individuals.