"Copy cat from Ballarat
Went to school and got the strap
Came home with a broken back"

- Anonymous

This age-old mantra is most frequently chanted by primary-school aged children in Victoria, Australia. It is generally applied in a taunting manner, to shame any such individual who is caught in the act of plagiarism. Such a person then becomes known as a "Copy cat". The reasons for this feline moniker remain obscure; as do the question of their origin: why should they originate in Ballarat (a small township in central Victoria)? Perhaps there was a valid reason for it that has been lost in the mists of time, but I think it is fair to simply assume that it was chosen for little more than it's rhyming value.
The second line hearkens back to the days of corporal punishment, long since abolished in Australian schools, but still known and feared by children through contact with their parents and others of earlier generations.
Finally the third line describes the severe medical trauma that can be incurred when applying a punishment designed for children to another species. This line, if I recall correctly, was not always recited as part of the mantra; evidently the dire situation illustrated by the first two lines was quite enough to strike fear into the hearts of would-be plagiarisers.
It is my theory, (unfortunately I lack evidence to support it) that this third line's origins begin in another simple children's verse:

"Step on a crack
Break your back"

This refers to a rather painful situation that will allegedly ensue should an individual be foolish enough to step on a crack in a cement footpath, or any cement paving material for that matter. Occasionally another, even more disastrous, scenario was described: some versions of the rhyme would have one believing that one's mother's back would be the one to suffer a fracture should a crack be stepped upon. It can be seen how easily a child would adapt the rhyme of "break your back" to fit in with the two base lines of the Copycat mantra.
In the course of my research I was able to also trace back a much earlier version of of "Step on your crack / break your back". After interviewing my grandmother I was interested to learn that in the days of her childhood the rhyme went:

"Step on a crack
Marry a black"

A shockingly racist comment, in that it implies that to marry someone with dark skin is somehow a degrading experience. What makes it even more shocking is the fact that small children were brought up with this racist doctrine; they simply didn't know any better. However, now we do know better, and we ought to be thankful that we have the opportunity to see that all people are equal, irregardless of their appearance.