Web Master:
Have you tried looking in the indoor plant section of nurseries?
You would be surprised with the scale some nurseries have and just how many plants can look like tropical/rainforest plants without actually requiring a tropical climate to grow in.
Given that the school is in Moorabbin, you are not too far from Garden World - that would be a good place to start, they could help you put your rainforest together in no time.
You'll need some advanced plants in large tubs, which won't be cheap, but it will definitely transform a drab, concrete space. Humans just love to be surrounded by greenery.