Gee whiz, your case sounds familiar. I feel like I've read the decision on Austlii, or maybe just one like it.
Anyway.
This is tricky, because you already have orders from the Court, which makes them difficult to change. Applications to change orders need to meet the Rice & Asplund threshold, which is that there's been a significant change in circumstances from when the orders were made, such that they no longer meet the best interests of the children, thereby warranting a change to the orders.
So, your first step is always to organise a family dispute resolution conference with the mother to negotiate changing the orders so that both parents are restrained from attending the children's school during their time with the other parent, except as otherwise agreed (and for extra curricular activities, if the current orders so permit her attendance at them).
Failing that, you could at least file an initiating application with the Court to vary the existing orders and let the Court decide whether it will hear the matter or not. This is a fairly discrete issue, so who knows? The Court might agree that mum's attendance at the school isn't in the kids' best interests based on historical behaviours, and it might make an order accordingly. Worst case scenario, the Court dismisses the application and you find some other way to manage this problem.
The alternative is to file a civil application for an Apprehended Violence Order (AVO) and include an order that she not attend the children's school except as necessary to abide the provisions of the parenting orders. You might have some success, given you have a ruling from the Family Court about the issues caused at school. Most people accept AVOs without admission, and if they contest them, they don't often have much luck.
Or, you could simply let mum do whatever she needs to do to make herself feel better while you move on and ignore her. It doesn't matter how often she preaches that you only won because you 'lied your way through Court' or because 'the judge was completely biased' or whatever, the reality is that you have sole parental responsibility and the kids live with you. Even idiots can't ignore that...
