Tertiary institutions say new league tables of their performance on measures such as course completion do not tell the full story.
The Tertiary Education Commission published the data for government-funded tertiary providers on Thursday.
Among universities, Massey is bottom of every measure, while the Open Polytechnic's qualification completion rate of 21% is the worst of any public tertiary institution.
But the assistant vice-chancellor at Massey, Cas Carter, says its figures are skewed because most of its students study part-time.
Without part-time students, Ms Carter says, Massey's rates are at the mid-point for universities.
The Open Polytechnic had a similar explanation for its figures.
