the discount will be autometically invalid from the second year, and combinating some other factors, that the second year's premium goes up to 10%~20% is not unusual. generally, some people go to get the G license to lower the increasing rate.
one factor resulting the increasing rate is that, after you get a job, the milage you drive a year usually is longer than that before your getting the job. this is a real possiblity causing your increased premium.