Over a million sport-related concussions (SRC) affect children annually in the United States, posing a significant public health concern. Limited data exist on the premorbid risk factors and injury characteristics of SRCs in high school athletes. This study aims to understand acute SRC injury characteristics and describe premorbid risk factors in high school athletes. Athletes (aged 14-19 years) from 19 central Illinois high schools participating in school-sponsored sports from 2009 to 2023 were included. Sports Concussion Assessment Tool evaluations were performed as part of preseason and postinjury evaluations. Injury characteristics, such as mechanism, setting, and symptoms, were described using all SRCs in the study period. Odds ratios (OR) were computed to determine risk factors using athletes with a baseline Sports Concussion Assessment Tool before SRC and nonconcussed athletes. In total, 4360 athletes were included (3953 without SRC; 407 with ≥1 SRC of whom 168 had a previous baseline). Overall, 24.2% of SRCs occurred in female athletes, and most SRCs occurred in competitions while playing American football (52.3%), soccer (20.4%), and basketball (7.6%). Blow/hit to the head was the most common mechanism. Headache was the most severe symptom (2.55 ± 1.51 [SD]), and symptoms of emotionality and nervousness/anxiety were significantly more severe in female athletes (P < .05). Students with previous concussions (OR 2.64 95% CI [1.81, 3.78]), previous hospitalization for head injury (OR 3.19 95% CI [1.9, 5.14]), headache/migraine disorders (OR 2.23 95% CI [1.29, 3.66]), and learning disabilities (OR 2.69 95% CI [1.47, 4.61]) had greater odds of SRC (P < .05). Lower odds of SRC were seen in athletes identifying as Black or African American (vs White) (OR 0.54 95% CI [0.32, 0.86]) and those attending larger (vs smaller) schools (OR 0.64 95% CI [0.46, 0.88]). Understanding SRC risk factors and characteristics in high school athletes is critical for developing prevention and management programs, guiding neurosurgeons in mitigating SRC risk, and informing return-to-play decisions.