Don't you just hate the smug perfect parent....
When my children were of a similar age, I had a job where casually taking a morning off was very easy, so I started going to these sorts of events. The school had a sequence of workshops through Y1, as I recall. I stopped going, because they were full of a mixture of sanctimonious show-offs and obnoxious bullies.
There were the people who were primary teachers but had gone part-time since having children, who took the opportunity to point out that they were professionals, don'cha'know, and as teachers knew far more about whatever the topic of the presentation was than anyone else, including the people giving it. They'd engage in obscure debates about the nature of phonemes, desperate to catch the teacher out (there's a thread over in Primary at the moment about whether or not "so" is a sight word, which has a bunch of primary teachers desperately trying to top each other) but also to show off to the other parents that they Knew, while other parents Did Not Know.
There were the aggressively aspirational parents who were secondary teachers and university lecturers, similarly gone part time, who wanted their children to be reading at three and viewed primary teaching as all a bit trivial, really. They would ask questions like "I'm concerned that you aren't teaching my son about negative numbers in year 1, because it seems so important to understand that the number line stretches in both directions" and look around them to check we all realised how how clever they were. The father who did this the most frequently, an alcoholic secondary teacher, appeared completely indifferent to the fact that his children were struggling desperately with the syllabus as it stood.
There were the slightly dippy mothers who regarded spending money on a haircut as an extravagance, a waste of money that could be better spent on their children. They would say things like "this is all very well, but don't you think it's more important that the children should be happy and playing?", a premise I'd be very inclined to support if it didn't mean that they'd then start talking to me about fucking homeopathy afterwards. A subset of those were Very Religious, and would always take the chance to make sure that the books being used that year didn't include The Books That Cannot Be Named. Yes, this was a school where, thankfully to mass derision, a couple of religious whackjob parents got up a petition about Harry Potter, who they wanted banned for various incoherent reasons but not because the books are baggy, badly written and dull.
And then there would be the relentlessly dim parents who would interrupt every presentation on maths to give their half-remembered accounts of being at school in 1976, the year in which (it would appear) arithmetical techniques reached their very zenith, since when all change has been decay (yes, the day they explained chunking was horrendous, since you ask, with the aforementioned alcoholic coming close to blows with the headmaster over long multiplication).
People outside these groups just cowered and let them get on with it, and as the year went by just didn't show up. The people that needed to know, or at least would have benefitted from being told, were driven away by a small hardcore of people whose every question screamed "I Am In The Room, You Know", and who either knew the answer already or were certain not to like it when they were told. It was, all told, a complete waste of everyone's time. I wanted to scream "shut the fuck up and listen" but, to my shame, just skulked away.