"Rachel is a young person who has made an outstanding contribution to her organisation, and her community, and has helped students achieve incredible outcomes," Institute of Public Administration New Zealand president John Larkindale said.
Mrs Tremewan leveraged the Government's Youth Guarantee Policy to double the student numbers during 2013-15.
She was "astounded" to win the prestigious award.
"The other categories were massive government departments so it's pretty overwhelming," she said.
By developing flexible funding plans, more than 26 schools throughout the Waikato are now involved in what is the largest trades academy in New Zealand.
In 2014, 75 per cent of students achieved 80 per cent of their credits and 87 per cent of all students remained at school or progressed to further education or employment.
Mrs Tremewan developed three new vocational pathway programmes for senior secondary school students and was involved with a three-day career pathway Youth Summit for 80 at-risk Year 10 students.