6 year old daughters finger almost cut off due to someone bullying her..?

my daughter goes to denver public schools..yesterday she was going to use the restroom when a child who has been bullying her slammed the door on her hand ripping her pinky finger almost all the way off..i took her to the er where they were able to put it back together..it was hanging on by only about a 1/2 in of skin and bone was exposed..luckily the bone wasnt broken but she probably wot have feeling in her finger and her nail will never grow back..my question is is there any way to keep this child away from my daughter..the school doesnt seem to take this very seriously..