Don't expect to see any change out of £3000 possibly as much as £5000 .
Teenage drivers are rightly seen as very high risk, over 1 in 3 will have an accident serious enough to need a claim inside the first year.
It is worth him taking and getting a 'Pass Plus' certificate, this is an extra course that teaches motorway and night driving as well as basic car maintanance. Almost all driving schools do it, it cost £150 but it is possible to get a discount on insurance that will more than pay the cost .