However, to prevent this, it will HAVE to be downloaded! But no one knows it doesn't have to be installed.
This is so easy a potato can do it! Just download the Maverick installer but quit it when it starts.
Be sure to keep it somewhere that makes it hard to click on to prevent accidental installation...
This is how I teach those who come in to the apple store who come to see me, want to prevent maverick upgrading.