No doubt the teaching unions have considered taking such an approach, and realised that it would almost certainly be counter-productive. The Murdoch papers and the other right-wing press (Mail, Express, Telegraph) would have a field day, lambasting these disgraceful teachers who punish innocent defenceless children for their own selfish ends, etc etc etc. Public opinion would quickly turn against them, and the teachers' campaign would soon collapse
Dave,
Apart from the bit about the Tory trio press I disagree entirely with your whole
assertion, public opinion would be divided. In fact that's the big issue now anybody that has anything to say or do that courts the slightest bit of controversy, in the very first instance before they do it, considers the stance of the press - exactly as you are doing, and that governs whether they will do it or not. Press reaction should be a side-effect of a stance not the reason for it.
Anyway, whatever our disagreements, you surely must agree that announced and spasmodic one day strikes by Teachers are a pointless exercise for them and will produce nothing for them only the loss of a day's pay and irritation from the public. Such "disputes" are just seen as a minor inconvenience that parents will surely learn to cope with very easily.
No, the reason the unions have not taken my previously suggested route is quite simply because the Teachers themselves have not got the bottle for it.
Probably because they have given too much consideration to the reaction of the Press.