The fair, at Kerikeri's Packhouse Market on Saturday, drew 26 high school teams from Awanui to Maungaturoto. All are taking part in a year-long programme in which students create a real product or service, set up a real company, and make a real profit or loss.
The trade fair is their first chance to showcase their products to the public and ring up some sales. The teams were judged on presentation, marketing and financial controls. Customers were also able to vote for their favourite business.
The judges awarded the top prize to Parakore, a Kerikeri High School team which makes cleansing tea from manuka, orange rind and kawakawa leaf.
Chief executive Shannen Frear, 17, put their win down to hard work.
"We believe you get out what you put in, and we've worked extremely hard to earn our success."
The customer choice title went to Hopu Ahurea, a Springbank School team which produces frames for 3D art such as wire sculptures and recycled LPs decorated with Kiwiana-themed stencils.
Wilson Baker, 18, said the company's aim was to provide another outlet for Northland artists and counter the sale of imported souvenirs. It also meant artists could focus on creating art while they took care of framing and getting their work into shops.
Concern for the environment featured in many of this year's student businesses.
Far North Possum Killers - with members drawn from Te Kura Kaupapa Maori o Taumarere, Whangaroa College, Taipa Area and Kerikeri High schools - builds rat, stoat and possum traps and has its own pest control area at Wainui Bay.
Money made from the sale of possum fur goes back into the pest trapping operation.
A business set up by students of Westmount School in Maungaturoto, Big Brother Surveillance, provides security equipment such as hidden cameras and GPS tracking for beekeepers, whose hives are increasingly targeted by thieves.
The team also had a stand at Fieldays, New Zealand's biggest farming event.
A few of the businesses on show on Saturday are already more than paying their way.
Whangarei Girls' High students Celina Yang and Ella Donald, both 18, hire out designer dresses and ball gowns in an online business called Borrowed Style which they hope will help pay their way through university.
Josh Burns, 16, of Kamo High School, is already having to turn down work because school gets in the way of his thriving aerial and events photography business, Up Imagery.
Any money he makes is invested in new equipment. Josh said the business could easily be his full-time job if he didn't have to go to school.
The Young Enterprise Scheme is sponsored in Northland by lines company Top Energy. The overall winners for 2017 will be announced at a function in Waitangi on October 20.
TRADE FAIR RESULTS
1 Parakore (cleansing tea), Kerikeri High School; 2 Hopu Ahurea (framed 3D art), Springbank School; 3 Big Brother Surveillance (security systems for beekeepers), Westmount School, Maungaturoto.
1 Hopu Ahurea (framed 3D art), Springbank School; 2 Double B (natural skincare products), Kerikeri High School; 3 Aqua Woods (spa pool boards for food/drink), Kerikeri High School.