I'm a primary school governor and have a dd at a state secondary (comprehensive).
It is certainly true that state schools are facing a funding crisis, and this needs to be addressed as a matter of priority. As governors, we have had to set budgets with in-year deficits for the last few years, and we are rapidly eating into our reserves. If we continue at the current rate, our reserves will be gone within three years. There is nothing left that we can realistically cut. I hear that secondary school finances are in an even worse state than primary.
There is also a teacher recruitment crisis. Teachers are leaving the profession in their droves. If the pressures on teachers are not addressed, this will get worse, not better.
Having said all of that, the primary school where I'm a governor is absolutely bloody fantastic. The children are happy, well behaved and excited about learning. The teaching staff are highly committed, hugely talented and very creative. The support staff are top notch. Pastoral care/SEN provision is excellent. The results are outstanding. The learning environment is inspiring. The enrichment opportunities are incredible. Although we have tried to communicate with parents about some of the financial challenges that the school is facing, I don't believe that the parents have the remotest idea how bad things are, because as far as they're concerned, their kids are getting an amazing education. A lot of this comes down to the professionalism and dedication of the school staff, who bend over backwards to ensure that the quality of education/experience for the children doesn't suffer. However, I don't believe that this is sustainable in the longer term because the impact on individual members of staff is too high.
I think the situation is very similar for my dd in secondary school. She has fabulous, hard-working and inspiring teachers for all but one of her subjects. (Sadly, her maths teacher this year is rather poor.) The behaviour at her school is generally fine, and any incidents that do occur are dealt with quickly and effectively. The school celebrates hard work and achievement, and encourages students to explore different options for their futures. There are lots of extra-curricular activities for enrichment and personal development. Overall, DD is happy, thriving and on target to get excellent results in her GCSEs. However, behind the scenes, I'm sure that teachers are under a lot of pressure and I've no doubt that school finances are very tight.
We could comfortably afford to send dd to a private school, but would not do so because she is happy and thriving where she is, and I do not believe that the quality of education is necessarily any better in the private sector, although the resources and facilities might be.