I know I’m late to the party, but my go-to refutation is “Ok, name one school that’s doing that. Go ahead and look it up on your phone.”
Then point out if a single school actually did have litter boxes for the kids the name of the school and everyone involved would be easy to find. It’s not something that could be kept secret: just one person has to say something – a kid talking to their relative, faculty, a parent, etc. Once that happened FOX, OANN, etc would be on that like flies on shit … and they would name and shame.
But they aren’t, because it’s bullshit.