I think the Iranian school bombing was pretty clearly a mistake, given its proximity to an IRGC base, and (IIRC) the previous usage of that plot of land for military purposes, suggesting an issue of outdated target intelligence. That compounds with the lack of a plausible motive, and numerous demotives for hitting it deliberately. Which is not to present the action as significantly less blameworthy; it's a heinous negligence. Gotta have dirty bits in your cache, so to speak.