"Eventually he said yes and I wouldn't be here if I didn't enjoy it. It hasn't been difficult at all and only gets a bit boring at this time of year when there's not much on [racing]. My manager, Oliver Oakes, has made the transition easier."
While most teenagers have no idea what they want to do, Armstrong had a plan and started racing karts in 2007. By 2010 he was mixing it up at the Kartsport NZ national sprint championship.
The following year he won the class and was second overall in the 100cc junior restricted category at the New Zealand school nationals.
In 2012, Armstrong was juggling study with motor racing, both in New Zealand and the US, winning the Kiwi 100cc junior restricted title along the way.
More karting titles came along and he moved to England to contest the European KF karting champs. Last year, while still 14, Armstrong beat some of the world's best karters at the final round of the European KF champs at Kristianstad, Sweden, shortly after finishing second in the Winter Cup in Italy.
This year he's moved up to contest the competitive KZ classes.
"The karting over here is ridiculously hard. In my opinion, the KZ1 class is one of the hardest classes before F1. The drivers spend 10 years in this category and are very, very good and I don't think most people in New Zealand know just how competitive it is.
"It's not so much how fast they are, it's about how they manage the weekend's racing and how to get the best out of everything by the end of the weekend.
"My teammate, Marco Ardigo, is 33 and a three-time world champion. He's always three-tenths of a second slower in practice but, when he gets to qualifying, pushes harder and puts it on pole. He's like many of the others - they can find two-tenths whenever they want to.
"This has been better than a season in Formula Ford or something like that for learning. After winning last year the step up to KZ has been hard.
"I can regularly qualify in the top four but the racing is so hard [rough and tumble] that the results haven't really come yet," he said.
More recently Armstrong took the next step in his career and has been testing and racing in a Formula Renault single-seater. He raced at the penultimate round of the Formula Renault 2.0 series at the Nurburgring track with a couple of solid results.
The Formula Renault categories use a similar chassis to that used by the Toyota Racing Series, which will stand him in good stead when he arrives home in December in preparation for the 2017 TRS championship.
TRS dates
Round 1: Ruapuna, January 14-15
Round 2: Teretonga, January 21-22
Round 3: Hampton Downs, January 28-29
Round 4: Taupo, February 4-5
Round 5: Manfeild, February 11-12