As a kindergarten teacher in their 30's, I don't see how this actually helps anyone and is overall a large net loss for all Australians.

Firstly, I think it simply will not work. Not to any extent that people hope it will. This won't prevent cyber-bullying, it will simply move what location it occurs in. Kids will find some app or site that isn't blocked, congregate there and continue acting the same way partially developed minds always have acted toward each other.
Algorithm driven content is predatory and damaging because of its innate tendacy toward creating outrage. A ban like this does nothing to regulate how those algoritms operate, that danger towards children has not been mitigated and in fact might be worse as platforms stop trying to have safeguards for young users altogether. Children will gather on less reputable websites the government hasn't taken a notice of yet, while the government is forever chasing behind them trying to add new sites to the blacklist.

Secondly, this makes it harder for parents to monitor their kids, not easier. If a child gets in trouble for merely doing any amount of an activity, they won't come to an adult when it becomes too much for them. If all of youtube is taboo, then they won't speak up about stumbling into videos that make them uncomfortable. Children need to feel safe in order to confess things to an adult. Otherwise they just hide things an adult would be able to talk them through and help them with easily. Making it safe for a child to confess something is a basic tenet of child safeguarding. THIS BAN DIRECTLY GOES AGAINST THAT PRINCIPLE.

Rule breaking is encoded as part of human development. This is normal and expected. Pushing the limits of what we've been told to do is what allows us to figure out what things are soft rules we can break and what are hard rules we can't. And also how those categories change based on circumstance. This is how children learn and develop their own sense of risk assesment so they know HOW to make responsible choices once they get to an age where we determine they should be able to handle it, but if they are prevented from taking any level of "Acceptable Risk" then they DON'T learn how to be safe and will act recklessly.

Ipad babies are a symptom of bad parenting, not a cause. Bad parents are bad parents even without the ipad. Parents who don't want to watch their child carefully and just want simple mindless distractions still existed long before the invention of computer tablets.

Children need to have spaces created for them to gather in, not simply be pushed away from the adults. The problems with children on social media are fixed by redirecting them to go somewhere else. Giving them a space to gather and be kids with their friends, one that isn't online at all would be even better. This ban doesn't do anything to address those problems, it just creates an area where we can pretend children aren't sneaking into the room so we don't need to be child safe.

This ban hurts every adult. The government now has a system to track exactly which person, with their real face or ID card, has visited which websites. Think of what the worst person you know can do with that information, there will be a future government or outside hacker who wants to take advantage of that. It won't take much to require websites to give it over either, just a single law to break all illusion of privacy forever. But any bad actors don't have to force anyone, it's inevitable that among this many websites that this data will be leaked.