I really do understand the immense disappointment of pupils who fail tests, particularly for seemingly innocuous things but I am amazed that they don't really understand why. Being safe on the roads is far more than just managing to get through a 40 minute test without doing anything outrageously silly or accumulating too many minor errors. It is about being in control of the car and being able to react safely to changing situations. This is far more than just learning a set of rules and regulations and is what examiners are looking for.
Many test failures complain that the fault they committed was minor and they should not have been failed for committing it and, on the face of it, it may appear that way. For example, failing to signal when moving back in to the left after passing parked cars on a dual carriageway. Is this a serious fault? Well I have seen it marked as such and also completely ignored. This is because driving is not about following a hard and fast set of rules; it's actually about doing the right thing for the circumstances that exist at that time. Yes, we can teach pupils what the usual action should be in a given situation but they have to think for themselves constantly and make decisions based on what they see around them.
I teach my pupils to do just that, to be aware of road situations and other road users and adjust their behaviour accordingly - it's called road craft and is essential for safe driving. I recently had a pupil who clipped the kerb driving out of the test centre and still passed. Why? Because her driving overall was at a level where the examiner could see she was thinking sensibly and logically and not just doing what she was taught - and no, I didn't teach her to clip the kerb. Throughout, she was applying road craft and the initial mistake was just a nerve-induced error.
Once reasonably competent on the road, I tell my pupils that they are driving the car and therefore they must make decisions about what to do in any given situation. After all, once they have passed their test and are out on their own, they won't have an instructor sitting next to them telling them what to do and making sure they are safe. It's their responsibility then and the sooner they get into the habit, the better.
This approach encourages the pupil to take complete responsibility for their driving so that passing the test is easy and driving safely is completely natural.