How long does it take to look at the coordinates programmed into the cruise missiles? Or to review existing satellite imagery for the location and other intelligence sources?

If this was a school (which seems likely at this point) and if this was a US TLAM that hit it (which also seems likely at this point) then we should expect a lot of casualties when it's hit during school time (which also seems likely). And yes, we shouldn't trust what the IRGC is saying.

I think I'm on your side but in this case the correct course of action for the US would have been to quickly own up to the mistake. There is really not a lot of ambiguity here. This doesn't seem to be a case like "shots were fired from the school window" or some sort of dual use with IRGC having offices in the school. If there was a reason for the targeting then presumably we'd have a statement about it already.

Mistakes can be made and are always made in war. Leaving this open like this is damaging to the war effort.