My dd is at an independent, started in year 9, and some of the comments don’t surprise me about fee paying parents. One of her friend’s mums emailed obscenities and used the most foul language to the Head when he politely informed the mum her dc would be better doing BTECs (which school recently introduced) rather than A levels. I think she also screamed down the phone as well. Another parent was upfront that she’d emailed the school almost 30 times in a 2 week period about her 2 children. I sat there trying to not look like a gold fish as this was discussed in front of me.
The couple of times I have ever complained to schools (both state) were for legitimate reasons, such as the head when dd was in primary school trying to force my dd into swimming with no adequate spotting. Dd has a seizure condition, where her heart stops beating. The pressure was immense and in the end the class teacher, who was very supportive of dd and me, watched dd herself for the half hour. Had I known the proper process, I would have escalated this to the governors etc as I ended up sending a series of very circular emails to the head, who wouldn’t budge.
Edit - to add, I was on the WhatsApp groups of both state and subsequently private parents. A few of the state school parents were very vocal and complained about a bunch of stuff. On joining the year 9 private parents group, I was relieved to see zero complaints… also about the same number of parents as it was just the same group from primary school. Dd is now in 6th form. I don’t think anything has been said on it since the group was renamed from year 11 to 6th form.