Well said Di. Ped, you have to look at each situation and act accordingly.
This was a bunch of school children joshing each other as they left school. They were not hostile or a threat, they were just having a laugh..... and they knew that's what I was doing as well. Sometimes, but not always, it is quite rewarding to join in rather than being remote or trying to ignore things.
They were still having a laugh at "Richard Head" when I got off six stops later.