Back of the line, no cuts!

Remember back in primary school when you would line up at the canteen and eagerly await to spend the change you spent your entire morning convincing your mum you reeeeeeally needed? Fidgeting restlessly as you watched the racks of sausage rolls or pies or even cakes slowly dwindle down in number as the line got shorter, kids squishing and poking you as you waddled closer to the front. And there would always be that one kid that tried to cut in, trying to get to YOUR cake before you could!
And you would shout "Hey! Back of the line Timmy, no cuts!"

Wouldn't it be nice to have such a system in place for education budget cuts?

It's naive to think that smaller class numbers are the only way for students to achieve a strong academic performance. It's also naive to dismiss the effectiveness of competent professionals.
You can have a class of one student and one teacher, and still have an ineffective learning environment if the teacher isn't passionate, knowledgable and engaging.

And contrariwise, a good teacher that is under pressure from large class numbers can be made ineffective simply due to lack of time and resources to accommodate each student. And if the students are unwilling to learn, that is a whole other Mad Hatter's tea party.

Cutting class numbers is not the solution to Australia's declining academic results.
Our population is only going to get larger, which means more students. More students means we need more teachers. So more money needs to be put into developing effective teaching strategies, and more support given to teachers in terms of adequate pay for the amount of work they do, and the quality of work they provide.

It's important to have a balanced student:teacher ratio, yes, but also important to have good quality teachers. You can't boil soup from stone.

"Dammit Timmy, I said no cuts! Kamehamehaaaaaa!!" - True story