wasn't there a recent investigation and initial confirmation by the Pentagon and NYT that the US was responsible?
of course the motivation and will is there for Iran to stage a "false flag" operation to damage the reputation of the US and present themselves as victims to the rest of the world, but the specifics of this case quickly dispel that notion, such as the school being adjacent to an Iranian navy base, and the school house having been previously used by the navy and only later converted to a school, as well as analysis of footage that confirmed the missile that struck the school was a missile the US has access to but Iran does not ... so it is far more likely the US just didn't update their intel and had old target data.