Are you for real? Of course it could get worse, A LOT worse. We have a very good education system and while there is always room for improvement, we're hardly at the bottom of the pile.
It's not blackmail talk at all, it's a balance. You won't improve the education system without incentivising people to take up teaching and if you remove the few perks that the job has you're less likely to entice fresh blood into teaching, which in turn will result in the education system as a whole suffering.
As for your annual review analogy, it completely misses the point.
Teachers aren't asking for a pay rise or a better pension. They are asking the government to uphold existing contracts which were negotiated to include a pay freeze and changes to their pensions in order to help reduce public debt.
Now the government is going back and saying you need to sacrifice even more resulting in an effective drop in pay and a smaller pension.
I'm pretty sure if you had an annual review and were told you were going to get a pay freeze and smaller pension contributions you'd be pretty angry. Then six months later your boss tells you that you're going to have to take even more of a hit you'd be livid!