As part of that he spends a weekend a month in ambulances on the Coromandel peninsula, and he continues to do tutoring and other St John activities on the North Shore.
He was National Cadet of the Year last year - he spent the $500 cash prize on textbooks.
For many young people, involvement in St John is providing a pathway into careers in healthcare.
McFarlane says he started thinking seriously about a job in paramedicine as he was finishing school.
He wasn't tempted to become a doctor. "Ambulances are much more exciting."
The qualification he will get is accepted by many other countries, including Australia and the United Kingdom, "so that will help with the travel I intend to do".
McFarlane says what he learned in St John, particularly by taking part in national competitions, helped him with the coursework.
"A lot of the first year content I had already learned, and there are also a lot of communications and leadership skills you get that meant I felt more confident coming in and experiencing new things."
He says the St John cadet programme is not just about first aid but also about being a leader and role model and living the core values of the organisation.
"St John is a massive lifestyle. You have to commit a lot of time to be part of it and attend a lot of events, but it becomes a family."
Jacci Tatnell, St John's community programme development manager, says St John has about 6000 youth members throughout New Zealand, starting with Penguins from 6 to 8 years old, the cadets from 8 to 18, and the leaders above 18. Members collect proficiency badges towards the Grand Prior's Award.
"There is a strong clinical lean so the caring and first aid skills are a big part of it," Tatnell says.
"There is also a strong leadership focus, so from 13 the cadets attend leadership training programme and learn how to write and deliver a lesson, how to run games, and communicate well."
Clinical competitions allow cadets to practice on simulated emergencies, and there are also opportunities to support sports or social events.
Other St John community programmes participated in by St John's 14,000 volunteers include a friendship caring caller telephone service, health shuttles, and a programme putting volunteers in hospital emergency clinics to provide non-clinical support.
She says having a Grand Prior's Award is viewed favourably by the tertiary institutes that run paramedic programmes.
"It indicates they have done skills training and have a level of commitment and dedication. It takes a good four to five years work, you can't just swan in and out," she says.
Tatnell says her own entry to St John came 25 years ago when she had aspirations to become a teacher.
"Part of the St John programme was about teaching young people, and I found that attractive. It gets in your blood," she says.
Tatnell says St John wants its programmes to lead not just into clinical roles but also into other organisational roles like information and communications technology, human resources and finance.
"We are looking at ways to create internships and clear pathways into clinical and non-clinical careers."
Recent changes have included improving the clinical qualification framework so youth members can complete an advanced first aid course at an adult level. It also means the skills and qualifications young people obtain through St John are better aligned with ambulance operations and events support, and allows a seamless transition into the adult St John context once they turn 18.
