Here's the thing. Public sector jobs have had numerous pay freezes over the last 10 years, as a result people are leaving the professions in droves and there is a serious struggle to recruit replacements AND to retain those who still work there. The staff who work in these professions are expected to put up with ever deteriorating conditions as the people who are suffering most are the patients/children/general public. The only way to get a proper message across is through strikes.
The issues in the NHS were not caused by strikes - ambulances were queueing outside A&E before the strikes started, patients were waiting 10+ hours to be seen, people were dying before an ambulance was even sent to them, there were not enough beds and the corridors were full of seriously ill patients as there was nowhere else to put them.
Teachers were leaving and still are in droves - many cannot be replaced as not enough new teachers are being trained and those who are often leave after a few years. Teachers are expected to be parents, nurses, social work and still produce high quality lessons when what little time they have to plan, prepare and mark is eroded covering for missing staff.
In England this is often solved by putting unqualified teachers in front of the class - many parents have no idea that the 'teacher' their child has is actually a cover supervisor or TA. In Scotland there has to be a properly qualified teacher so classes are put together, staff lose planning time to cover and in the last few years its certainly not unheard of to have to put several classes together in the hall, or leave senior classes uncovered (16+)
Some classes might not have had a proper teacher that's not cover for months or even years. Many schools are dropping subjects at secondary since they can't recruit staff for it. And the staff are getting home at 6pm having taught all day, had no planning and prep time, meetings after school and still need to do their marking and prep for the next day.
To be a teacher (in Scotland at least) you need both a degree and a post grad and a year as a probationer (secondary school) to get paid considerably less than you would in industry, to be sworn and assaulted on an all to regular basis, to have endless reams of paperwork to complete and then still have parents bitching that they only had 10 minutes at parents night and that teachers should be responsible for teaching everything from how to tie shoe laces to how to fill in a job application form.
I can't afford to strike, but I certainly can't afford not to strike. If I was 18 again I absolutely wouldn't go down the teaching path and I love teaching. Right now, if something doesn't change I will be yet another ex-teacher within the next couple of years.