There is a crisis in education. I actually think it's time for schools to stop papering over the cracks.
Work to rule, strikes if necessary.
Teacher workload and wellbeing is linked to the quality of the education children receive. Parents need to understand that.
If I have no planning time in school because I'm covering absences and they can't get supply, I don't have time to prepare the great lessons I'm capable of. I don't have time to sit at lunchtime to help the child that is struggling with work or home or friendship issues. I don't have time to meet my basic needs for food and toilet, never mind anything else.
If they can't employ a maths teacher, because no one wants to put up with the conditions, and they can earn more for fewer hours, then you get a PE teacher covering maths. Don't blame the poor PE teacher.
If I'm overworked and badly treated, I don't feel like running trips, or organising special events, or extracurricular clubs, or after hours tutoring, or any of the other "extras" that make a great rounded learning experience.
If they can't persuade enough graduates to enter the profession to fill the gaps, they have to keep lowering the standards of who they will accept onto teacher training.
Improving conditions for teachers = improving your DC's education.