As has been astutely pointed out on this subject in the past, charging "bad" drivers higher premiums is tantamount to issuing them a licence (albeit an expensive one) to continue being a bad driver.

The higher premium should be accompanied by a requirement to complete successfully and accredited safe/defensive driving course within a specified time frame (say 6 months), failing which the licence is suspended for an initial terms of 6 months (with increasing terms thereafter).  Couple that with a mandatory 30 day jail term if convicted of driving while suspended.