While previous research has noted the large numbers of school personnel with exposure to potentially traumatic experiences and its relation to secondary traumatic stress, it is unclear how different patterns of adverse childhood experiences influence secondary traumatic stress. As such, the present study employed latent profile analysis to examine natural groups of adverse childhood experience (ACE) history in 218 school mental health professionals (65% female; 55% White, 17.9% Black; 39% early career, 34% midcareer, and 28% late career; Mage = 32.91) and 348 teachers (80% female; 80.5% White, 6.3% Black; 16% early career, 14% midcareer, and 70% late career; Mage = 41.03) to examine the magnitude of secondary traumatic stress. The present study also examined the moderating effect of trauma-informed practice efficacy on the relationship between ACE history latent profiles and secondary traumatic stress. Four latent profiles were revealed among school personnel: (a) low ACEs, (b) average ACEs (c) neglected, and (d) high ACEs. Additionally, trauma-informed practice efficacy did not moderate the relationship between ACEs history profiles and secondary traumatic stress. Implications include targeted approaches for helping school personnel decrease secondary traumatic stress. (PsycInfo Database Record (c) 2023 APA, all rights reserved).