I have no idea how the kids here in Australia say it but back when I was in kindergarten and primary school in Malaysia, there was a lot of "I don't friend you anymore!" thrown about.
Some days, Aaron comes back from school and says things like "Amber was my friend today" or "Ben wasn't my friend today". Today, it was "It looks like Freddy and Hudson are starting not to be my friends anymore." I know these are his words and I do wonder what they say or do to him that makes him tell me this. When asked, he shrugged his shoulders and said "I just feel it." Thankfully, he doesn't seem hurt or disappointed.
I'm not worried about him (yet). I know that this is a natural part of growing up and he'll figure it out. After all, I was one of those mean girls that had a first best friend (and a backup second best friend) and would frequently use friendships to my advantage yet I think I've grown up to be a decent person in terms of being a friend.
Nevertheless, its strange how human beings start off being completely alone and not needing any friends (except mom). And then, maturing to having a curiosity for other people of a similar size. Finally, they actively search for someone, anyone, to become 'friends' with only to then pick and choose which ones to share a friendship with and turn that status on and off depending on benefits.
The scary thing when I observe the children in the playground is that they are brutally honest with each other and have not yet developed any tact or sensitivities in dealing with people they no longer want to be friends with. On the practical side, it does make things a whole lot easier - none of that tip toeing around or avoiding people you don't want to hang out with. Still, as a mother, I had to give Aaron the whole speech about treating everybody politely and equally and not worry too much about whether or not somebody wants to be your friend.