It would certainly cause someone to take notice and might get the LA involved to ask some questions.Have you been in touch with Ofsted? They are the ones that can put the school into special measures, and maybe then get this sh*t show sorted.
One of our neighbours used to be a specialist teacher that got ‘parachuted’ into NorthEast schools that were underperforming to help turn them round. Her speciality was maths, and she has since left that occupation, but there are other specialists, not just teachers, that can be sent to schools to take over and sort them out - but Ofsted can only help if they know of the problem.
If NDA is in denial, and trying to hide the problems rather than sort them out, then Ofsted need to know. I’d encourage all of the parents with kids being bullied to get in touch with Ofsted, the odd case here and there might not gain much traction, but if it can be shown to be endemic, they’ll be obliged to get involved.
Best of luck.
Ofsted are used to 'co-ordinated' attacks from parents though, so unless there is a significant safeguarding angle, I would suggest it would be the LA who would get involved in the first instance.
Worth complaining to them too.
For what it's worth, I've had to deal with a number of enquiries from the LA regarding disgruntled parents, but never one directly from Ofsted.