It's got nothing to do with the school principal really - It all comes down to funding.
In the government system, the school finding primarily comes from the state, depending on where the school is what special needs there are, usually around the 11 - 15 k mark per student per year. This is spread across the school - internet bills which are expensive (my last school in Australia it was 30k a month for k-12 school with a population of around 2000 kids), power bills, resources etc. seems like a lot but it is bare bones really. By contrast my individual budget for PD at my last school was more than some departments can spend on resources in the public system so the amount of money each teacher is allocated is pretty small, and in some departments as little as a few thousand bucks a year can be allocated to departmental resources.
The private system funding on the other hand is federally based. Despite the fact that parents pay taxes to the state in the many different forms, the state spends very little on private school kids, usually around half of what it spends on public school kids.
So the budget allocations are different and in many independent schools, the principal or the board of directors okays spending based on a whole host of factors. It does strike me as strange that a teacher feels compelled to provide so much out of their own money - I am thinking that there is a budgetary issue there somewhere. It is definitely not a healthy school in that case and my view would be to seek an exit strategy.
As for the principal's pay - 120k isn't very much for a head of school - and this clearly demonstrates the lack of funding for education in Australia. Consider that the top independent schools in the country pay the principal upwards of a million bucks a year with a bunch of associated perks, 120k shows the disregard the government has for school leadership in public schools in australia.
Now in the international school system (for many years thanks to the terrible conditions in australian public schools), I can confirm that many classroom teachers earn close to 120k after all taxes have been paid in parts of asia, on top of free housing, three months off a year, and a cheap cost of living.
This also tells a lot about the attitude of the various Australian governments towards recruiting a keeping the best teachers - would you work for 75k a year, pay the ridiculously high cost of living and exorbitant tax rates in australia or go somewhere where teachers are respected, particularly australian teachers, paid what they are work and can save 75k a year?
If you pay administrators peanuts, and fund schools inadequately, you will always get administrators who have to make hard choices about where to spend and teachers who will pay out of pocket for their students. It's the nature of the beast unfortunately.
