I agree 1000% with Yabbers - and OP.
This thread is really sad to read, if it's all true. Why have kids if you don't want to be involved in their life and celebrate all the little things. Some of the posts even sound downright neglectful "yeah, my kid left PS but I didn't give a fuck, I was off on a cruise". Jesus christ.
Leaving primary school IS a big deal, it's the end of an era and signalling that childhood is on its way out and they've been in that class with those kids for years and some will be going to different schools. It's the start of a new chapter and growing up.
On my last day of primary, we had a massive, massive water fight in the playground when our parents came to pick us up, some even joined in! - huge deal water bombing parents and teachers - and then we went to mcdonalds. This was when mcdonalds, or any takeaway really, was a treat and you only went for birthdays etc. I can't remember if we had a disco, we probably did.
Don't listen to the miserable fucks on this thread op, the way you parent sounds lovely.