My DD has just left primary school and I have never experienced anything like what some of you talk about. I have made a solid group of friends and we have experienced births, deaths, divorce and everything in between over the last 7 years. We have also had arguments and times when we get on each others nerves but we apologise and move on.
In addition to this group of friends, I have always chatted perfectly happily to any other parent who crossed my path and have been out for coffee or days out with my DD and her friends and their mums with no issue, even though they are not in my main friendship group. To celebrate the end of year 6, me and a few of the other mums organised a party, some of the mums were from my group of close friends, others were not but we all worked well together and as other parents dropped off for the party, I had a chat with them too. They are all just normal people!
I do not know where this clique thing comes in or this Alpha Mum thing? I'm absolutely sure it must in some places, because of the posts I see on here but I feel very lucky that my experience of the school gates has been a positive one. (I haven't actually been at the school gates for a few years due to my work but have maintained contact with different people via my DD friends and at school events).
Finally, I really hope, if you never help with any PFA event, your child never gets to use the ipads or the books or whatever else that money has been used for. Yes, they need people to give money to buy things at the events but they also need things to buy and people to sell them. Our summer fayre was nearly cancelled this year because not enough parents volunteered to help on a stall for just one hour. This is our biggest fundraiser and has raised many thousands to purchase educational equipment, and parents couldn't stand on a stall for an hour! It absolutely shocks me. No one is saying you have to throw yourself in, attend every meeting and become a fully fledged PFA member. But offer your time, bake some cakes. Its for the benefit of your child. As others have said, the middle ground works well for most.