I suppose then the next bun fight is going to be over what constitutes 'half of school holidays' under current bio measures, & if schools are closed for months how you would interpret the beginning & end of school holidays..... That is why I think (in the absence of any agreement to do otherwise) you should go by the gazetted dates for school terms....
I suggest that it's a straighforward (well, straightforward for lawyers) question of statutory interpretation.
You start by remembering that things don't change, unless they change.
The variable here is not the order, and not the parent's conevenience/ wishes/ rights etc.
Next , you look at the plain and ordinary meaning of the words, and, if any there are express ones, at dates.
For example, if the School Holidays start a week early, then, unless there are orders that expressly say so, the start date of the school holidays is the new date.
Then (assuming that there is no change to the back to school date) half is whatever half is. *
But, if an order says "5 April" (or whatever), or something like
"The Tuesday before Good Friday", or "On the first day of Ramadan", or
"the Thursday before the June long weekend", then that's that.
This is different to a school having extras "pupil free days".
Those are term time - even if there's more of them, and even if they come in the last week of term, or the (would-have-been) first week of the next term.
Also just to chuck in another curly.... if Vic goes into lock down (very likely) the idea is that whoever is in that household at the time, REMAINS within that exclusive 'bubble', I imagine for at least 14 days... Interesting times
Two ways to approach that.
It would not be a breach of an order to keep kids at Parent 1's place due to a Public Health Order.
Nor would it be a breach of a Public Health Order to drive the kids to Parent 2's house, in compliance with an order.
Stuff is never interpreted in a way that requires somebody to commit an offence of breaching one, in order to comply with another.
Note that that's a pretty arcane concept, and your average Plod On The Street may not remember it from their training.
-------------------------
* Of course, if/ when schools close for an indefinite period, then there will be a more complex question to deal with.