It's in the wikipedia notice, if you ever tried to search it:

https://en.wikipedia.org/wiki/2026_Minab_school_attack

"According to witness accounts verified by satellite-based analyses, the school was triple tapped by three distinct strikes."

War crime isn't just a legal definition, just like the world was genocide-free before WW2. And by your reasoning it's totally fine to genocide people as long as no treaty/law prevents it. Of course it isn't.

Most people would agree to say that bombing a school or a dessalination plant is a war crime, whatever the convention was signed before. Schoolchildren are not responsible for the IRGC's actions.