I go to an Australian school, so I will say my views to anyone that is interested.
At my school (northern suburbs of Perth in Western Australia) there is no or little selling of pirated movies. Some people have pirated DVD movies from Asian countries, but as far as i know they don't sell them to other people, although they freely lend things. Pirated or 'burnt' computer games are another matter though. Everyone burns games, its like an accepted thing, and it is fairly rare that someone will buy a proper game unless they REALLY like or want it. Also these burnt games are really bought, they are done by anyone with a CD recorder for free or the price of the blank CD.
Its exactly the same as PC games with music. Everyone burns music cds instead of buying them, or they are 'made' from mp3s downloaded from the net.
Also, I believe the issue of 'children' getting cheap pirated movies with an R rating is nothing to be worried about, at least in my school, however any computer game of any rating is easily available......