No testing stations operate in Hawkes Bay during the weekend and Amundsen said she had 13 phone calls yesterday from young people who had left it too late.
Leah Edwards of the Waitakere Testing Station noticed a steady increase in the lead-up to the new rules.
"We usually have one or two 15-year-olds through each day but we've had four times as many in the past three days. It's been horrendously busy."
Mt Eden teenager Georgia Ramdin turned 15 on Wednesday but waited until Friday to make a booking at her local Kingsland VTNZ station.
She was lucky to get in before all time slots were snapped up. Ramdin said she studied for three days in preparation and practised on the internet.
A few of her friends weren't old enough to make the deadline and were gutted to have to wait another year.
AA spokesman Mike Noon said the increase in age was likely to bring a slight improvement in crash rates but international evidence indicated supervised training mattered most.
"The best thing parents can do when their teenager is learning to drive is ensure they clock up 120 hours or more in all driving conditions under the eye of a supervisor before going solo."
The law change will affect 15-year-olds with a learner licence as they will now have to wait until they are 16 to sit their restricted licence.