NYT did an excellent analysis showing that the US probably did intentionally target the building, believing it to be part of the nearby compound that received several direct strikes. This analysis is really good [1]
The definition of war crime is not "Killed civilians" it is "targeted civilians" or "reckless indiscriminate attacks". My understanding of the NYT analysis is that this was very plausibly misunderstood to still be part of the iran national guard compound.
Everyone gets their own opinion on this. There were 900 or so strikes in the first 12h, and only one school hit, and that school was actually part of the compound before. A horrific accident that was brought on by unnecessary hostilities, i think.
1: https://www.nytimes.com/2026/03/11/us/politics/iran-school-m...