Every school is going to need casual teachers to cover classes while the usuals are sick/training/sports trips etc.

I know maths is needed for secondary in NSW these days, but that's probably not much help for what he has studied.

You would be surprised at the number of teachers that appear to be permanent, but are really on a contract type system that gets renewed year to year at their school. A lot of these are because if they advertise a permanent position, there might be someone on a transfer list that the school is forced to take. So if they just make it a contract, they can get who they want. People get these contract positions by doing the hard slog at being a casual and the school seeing that they are a good teacher.

I've got something in my head that only 10% of graduates move directly into a permanent position in the public system straight out of uni - don't quote me on that though! The rest may move into Catholic/private and then heaps into casual/contract type.