The scheme, which Weltec partnered in 2010, had launched the preceding year as a New Zealand-first pilot.
Other sponsors include Genesis Energy, Masterton District Council and the JR McKenzie Trust.
Mr Morunga earlier told the Wairarapa Times-Age that 30 mostly at-risk teens had initially joined the scheme in February after having either quit classroom study or been referred by schools in the region.
WelTec tutor Bruce Oliver, who has been at Te Heru a Rangi since 2010, commended the 20 Level 2 and 3 trainees who had remained despite the absences, court appearances and arrest of some of their fellow students.
Mr Morunga said he was heartened that a majority of the Level 2 graduates this year had promised to return for Level 3 training if they were unable to find work over the holiday period.
"This is a great outcome for us. The Level 2 students have watched the house going up and reckon they can do as well or better. And if it takes friendly rivalry to get them back - all good."
Level 2 students have worked over the past year at the Ahipanepane Urupa and have rebuilt fencing at the Te Heru a Rangi centre during their course syllabus, which also includes roofing, plumbing, numeracy and literacy.
Mr Morunga said helping get jobs for trainees is a renewed focus on the scheme along with pastoral care that Weltec provides for trainees alongside Nga Kanohi.