It is not KKK , but unless it is a all black school I feel a all life's matter is more appropriate otherwise what message it that saying to the kids.
The complaint you and other make about BLM with the all lives matter is like the following.
Its like driving down the road & seeing a man holding a "Save the Whales" sign. You slam on the brakes & scream, all life matters.
BLM is about the killing of young black men by police or others & having no or little investigation. Like Trayvon Martin, Zimmerman kills him & police just believe Zimerman's story, they don't even bother with proper protocol. A black guy selling illegal cigarettes is killed by police & nothing.
Just like "Save the Whales" does not mean they are the only lives that matter, BLM does not mean just black lives mater.