The main source in that Wikipedia article is "According to the IRGC." Trusting any belligerent in a war is silly, but given its history, trusting the IRGC during wartime is even sillier. No independent body like the Red Crescent (which is counting casualties in Iran) verified this. It's all "trust me, bro."

USCENTCOM and the IAF both rejected these assertions.

You should demand some evidence for the IRGC's claim. If the claim is that the US or Israel did it, why doesn't the IRGC show the munition used? Or any OSINT data, like where the munition was fired from, its trajectory, etc. The IRGC has been firing from the IRGC base where this school was located. It could just as easily have been a failed IRGC munition.

Also, was this "school" by an IRGC base actually a school, or did it serve a military purpose? Surely you can't know the answer to this, so it's tough for you to judge the military necessity of the strike.

Finally, what's the claim, really? That western powers intentionally struck a school and killed these kids to advance their war aims? Or that it was an accident? If the former, an explanation for "how" is required; and if the latter (and if it did indeed happen) it's the kind of collateral damage that occurs in all wars.