I'm surprised you're allowed to do that in the first place. I'm not a teacher, but my impression of school systems in the West (and first-hand experience in Poland), is that standardized testing, standardized everything, and whiny parents, pretty much force the teachers to teach to specific, detailed curriculum, with little room for any experimentation in approaches.
The little teaching I did, was on the private side (courses in computer use, 2D graphics authoring, and similar), so it was up to me to make it work - I didn't have a curriculum I was mandated to follow.
> I can only speak for Australia, but here "teaching from the textbook" is highly frowned upon.
Even more surprised by this. Positively surprised.
Over here, the material changes yearly, too. But it's not the teachers changing it - it's the textbook authors moving some things around, to force parents to buy new books each year instead of reusing the ones they have (or getting them from second-hand sources); the changes are made specifically to make life miserable for a teacher who allows multiple editions of the book in class, and thus using the teacher as proxy to pressure the parents.
Needless to say, this makes me extremely skeptical about any year-on-year curriculum changes, particularly when they involve students/parents paying for the same thing multiple times.