unfortunatley you just have to bite the bullet and pay up. I paid over £2k on my first car when I passed at 17 which was a complete banger but you're not paying for covering your own car you're paying for the potential damage caused to other vehicles or people if you do crash. As young drivers in the first year of driving are statistically far more likely to crash then the premiums reflect that.

Get him to do Pass Plus which should save a few hundred quid and once he's got a years no claims under his belt you should see the premiums come down. You could also try putting yourself or partner down as a named driver on the policy which can sometimes bring down the costs.