Lisa, here in Australia we refer to substitute teachers as relief teachers. So when I use the term relief, it equates to your 'supply'.
But for going back to my old school because they were desperate at one time, I have always said I would never do relief.
What I witnessed over my years of classroom teaching, was relief teachers being so abused, being loaded with extra duties, given the class from hell, many of them having no idea about employable strategies that don't always, but often work.
What happened in your daughter's classroom doesn't surprise me in the least. Many classroom teachers adopt such stringent management strategies, so that they students end up being wound up like clocks. AND, as soon as some kids realise that they are having a relief teacher, it's party time!
Of course they wait until the coast is clear.
That's when the bullies come into full force. They scare the living daylights out of the rest of the class, so that, even when damage is done, as in., your daughter's eye, everybody is too scared to rat on the perpetrator of the incident.
I can only try to imagine your anger at the injustice of the court case. They could have done so much more..
But also there's certainly a high level of culpability on behalf of school management. They KNOW the classes that play up. They know where problems lie. There are things that could have been done to avoid the tragedy that occurred.
Therefore they have a duty to the students in the class and to the relief teacher. To that end, doors are kept open, no pictures on windows for obvious reasons, bullies are given a new, short-term 'home', and a neighboring teacher is always on alert.
On that day your daughter was bullied and injured, as were the rest of the decent students and the relief teacher, because while bullying doesn't always leave visible physical scars, it sure leaves long-term psychological ones.
I doubt the relief teacher ever worked another day as such. She was probably young and inexperienced. I know exactly how I would have handled the situation, but that 'knowing' comes with years of practice!
Teaching was hard ten years ago. These days, who knows, but that there's such a staff shortage now, isn't just because of the shitty pay.