You will be investing a good deal of money in your driving lessons so when comparing prices it is important that you understand a little about driving instructor qualifications and just what you are getting for your money. For example, are you aware that many driving schools offering cheap lessons use only partly qualified or trainee instructors (PDI’s)? Although this practice is quite legal it is rarely made clear to the student that they are being used for the trainee to practice on. It is also a fact that the chance of passing your driving test with a partly qualified instructor is significantly less than with a full qualified instructor. (ADI) When teaching, it is a legal requirement for the instructor to display his licence in the front windscreen of the vehicle.