Having police trained dogs in public schools enforces a way to reduce violence. So many schools these days are filled with violent youth and they think that they can get away with everything but having the police trained dogs present in schools will kind of make students scared and not want to act out.
As accidents always happen any time, humans especially are not gods that never make mistakes but as dogs, they have a small brain. Who knows what K-9's could do? They may look cute but "don't judge a book by its cover" Animals can be dangerous but why would you want dogs in your school? There are small children there for what? For nonviolence teachers can handle that.