There were apparently some schools that had cat litter around because children can’t go to toilets during school shooting lockdowns, which is terrible in its own way.
I think that’s also made up propaganda. Kitty litter is used by janitorial staff basically everywhere (at least in the US) to clean up vomit and other semi-wet solids. Children are prolific pukers so it’s not surprising that basically every school has a bunch of kitty litter in their janitorial closets.