@freckles20 your statement
At the moment only children educated in the state system are disadvantaged by the unfit system. Disadvantaged not only in terms of education but also in terms of mental health and so many other things.
Is part of why the system is broken, if parents expect the state system to be broken, those that can afford it will give up and go elsewhere such as the private system, those can't may give up and say 'well that is to be expected and there is nothing I can do about it'. I've seen great schools at work. My daughter is in one of them, yes it is a grammar school but I have friends which DCs thriving in comprehensives in affluent and deprived areas. Making sweeping statements like this is not helpful. As a parent I've been to spruce up days to paint walls, sand down science benches, local and national businesses have contributed all sorts of things from skips and paint to plants and spades. It has created a great community spirit. I know some great Parent Governors who make great contributions to the schools they volunteer with.
Yes there will be people who say 'but schools shouldn't have to do this' but again that is being defeatist and ignoring all the amazing things that can be done in, with and for state schools. School accounts should record all this sort of hidden funding and the value of volunteer work (down to teachers supplying glue sticks that we often hear about) so the state can see what level they should be funding to, not what they are getting away with.
I also know pupils at private schools with far worse mental health than those at the local state schools, the pressure on the private educated is keenly felt by some as the parents want to see 'it was worth it' and the drugs and eating disorders are hideous.