No rules for kid ?

I work in a retail store in Adelaide. There are some kids ( 12-15yr)who comes to steal stuffs. Shoplifting is not my issue they not only steal stuffs they throw cans of drink to staff or do something to ruin our entire day. A kid came in with water gun and sprayed it to one of my workmate and ran away again he came back later saying how does it feels to be sprayed pee all over your face? Complaints have been made several times to police regarding this kind of behaviour but they do nothing and it’s too frustrating . We can’t do anything cause they have got way too much rights. Any suggestions?