For what it's worth, I am also very concerned about covert recordings being made of teachers.
I am very concerned that making covert recordings is the only way of evidencing what is currently going on in schools.
There's an active thread on the sex and gender board at the moment where a poster says that her son used his phone to take covert pictures of some slides - not a teacher, slides - to show the nonsense they are being taught about sex and gender in RSE, and he was caught, forced to hand over his phone and unlock it, the pictures were deleted, and the mum was called into school to discuss the incident. And even after all that, the school wouldn't let her see the slides or even tell her what her son is being taught about sex and gender.
Why the secrecy? What are they hiding?
Can you think of a single other subject kids are taught at school where the policy is to deliberately conceal what children are being taught from their parents?
This is a classic tactic used by paedophiles.