But taking on 50 students this year means it will have to take on a further full-time tutor at its carpentry school at No 3 Line. That will give it four full-time and two part-time tutors.
The courses run for 44 weeks and the new students should be starting their courses before the end of this month.
"We're advertising flat out for these extra 50 places and that's not just locally," said Mr Macdonald.
"We're doing that because similar courses, for example, in Palmerston North ... cost about $5000 while ours is only $850," he said. "We see a reasonable fee as allowing a buy-in from the students."
The trainees graduated with a "local certificate" which Mr Macdonald said had earned "huge support" from the building industry over the past decade because it focused on the theoretical side of a building apprenticeship.
"Rather than doing the practical work as an apprentice then doing the theory at night school, our courses are 50 per cent theory and 50 per cent practical hands-on work.
"It means when they leave us they can go into the industry and concentrate on their practical apprenticeship because the theory side of it has been signed off. It takes out about a year off the four-year apprenticeship," Mr Macdonald said.
"Industry is now turning their apprentices to us for that initial learning."
The practical aspect of the courses happens at AG Challenge's depot in No 3 Line where students are currently making three-bedroom relocatable houses for Brittons House Movers.
Mr Macdonald said under this arrangement Brittons provides all the materials with the students providing the free labour as part of their trade training.
"Last year we started building relocatable classroom for the Ministry of Education because the ministry recognised a number of their schools did not meet the earthquake codes.
"This arrangement with Brittons is not in competition with local builders but simply gives us the training ground.
"It's good for the city because it's about attracting students to study here in Wanganui. We're not putting kids on a bus and taking them to Palmerston North to do their courses," Mr Macdonald said.
Whanganui MP Chester Borrows congratulated AG Challenge on its successful tender.
"AG Challenge has been working hard to provide high-quality graduates in the trades sector for some years in our community, and it's great to see that paying dividends for them," Mr Borrows said.
"The reconstruction of Christchurch and Canterbury will have spin-offs for businesses throughout the country. Our challenge in the North Island is to grab whatever opportunities arise, and I'm thrilled that AG Challenge has been able to do just that."