My previus airline told me that we had to brief them and tell them that they could evacuate once the majority of passengers had evacuated.
I can only assume this is because they will be holding up everyone if they went first. Discrimatory yes...
When they evacuate they will have a crew member cross armed with them behind them on the slide.
They are instructed ONLY to go out through a floor level exit. Ie. No window exits.
They are given priority on boarding however, they are not given priority should an emergency situation occur.
There are so many what if's in this industry. It can be disheartening because crew are instructed not to risk their own life or go back into the plane if there is immediate danger...now with the disabled evacuating last...they may need to be left behind. Let's hope that never happens.