Last I heard of the HAT was external assessors come in and assess your lessons etc to determine if you are HAT. It is not a simple viewing, but it is almost like a portfolio. The teacher has to pay for the assessors to come out and if they don't 'pass' then they still foot the bill.
AFAIK in the next couple of years, all teachers will need to accredited and maintain this accreditation every 5 years through professional development. HAT are additional to this accreditation.
A HAT will be part of the executive, but only on half a teaching load, remainder of the load is to support other teachers.
I have a very superficial understanding atm, but I will be finding out more as I will endeavour to be one of these in the next few years.
At the moment there are very few HAT in the state. I can't remember the exact number, but it was around 10-15 last I heard
That isn't what this is about it is about teachers displaying that they know what they are teaching deeply and being able to teach it effectively not based purely of exam performance otherwise poor performing areas will have chronic shortages of teachers as they all compete for the more accomplished schools
Most of the best teachers I know are at lower ranked schools. Some teachers at high ranked schools don't even teach.. At least according to my tutor students.