Most private schools won’t let members of the public use their ovals without a definite connection to that school. There are some very well maintained school ovals that would be amazing for sprinting on!
Synthetic Hockey pitches are also amazing to run on. Often softer than rubber tracks and firmer than most lush grass ovals.
There seem to be more of the same synthetic surfaces at soccer grounds. One in particular at the The John Cain Memorial Reserve on Darebin rd, Fairfield in Victoria. There are two joined together where you could easily get out a straight 150m!