Does insurance go up if you have failed your driving test before?

Insurance companies take into account your driving experience (ie how many years you've been driving + how no claims bonus you've got) but not how many times you've failed your test before getting your licence. It is actually irrelevant unless you've been asked to retake your driving test because of disqualification which is not the case here.

Has your son done a Pass Plus course? He can get upto 40% discount with this course.

i agree. pass plus tied in with those specialised young drivers companies are the way to go. also you'll pay thru the roof for a car than is only a few years old and is more than a 1 litre. choose an old car (10+ years) and the price should come down some. also these days, there is not a lot of difference between comprehensive and 3rd party. its worth going fully comp and start building those no claims from an early age.