Are you a qualified instructor?
Yes. In order to conduct driving lessons on a professional basis, all instructors must be registered with the DSA.
Some schools use 'PDI's (practising/potential driving instructors). These are registered instructors but who have not yet passed the final part of their instructors test. These will display a pink triangular sticker in the car window.
I am a fully qualified instructor and as such, display a green, hexagonal sticker in the car.