International student numbers are likely to drop as tweaks to post-study work rights come into force.

Under the new changes, students who study high-level courses will be offered three-year work visas, while students studying less sought after qualifications won't be able to work in New Zealand.

Immigration Minister Iain Lees-Galloway told Mike Hosking students will be more selective in what they study.

"Some won't come, some will change their course of study, some will go to university rather than study at sub-degree level."

He says student numbers could fall by as much as 6000, however he thinks a drop of 1200 is more realistic.

LISTEN ABOVE AS IAIN LEES-GALLOWAY SPEAKS WITH MIKE HOSKING