Tighter regulations on international school providers are helping the industry's reputation among visiting students. (File photo)

Four international schools across New Zealand have been closed down and many more put under tight restrictions since a regulation overhaul.

Sector leaders believe the changes have improved, not tarnished, the reputation of the country's $1.08 billion international student industry.

Providers like AWI International Education Group, International College of NZ, and Cornell institute recently lost course accreditation due to concerns over assessment capabilities, and two more are being monitored over similar concerns, the New Zealand Qualifications Authority (NZQA) website shows.

Last month, NZQA also filed criminal prosecution proceedings against an unregistered private training school and its director, after international students were allegedly enrolled illegally.

The closure of the Retail Business and Management College (RBMC) in Christchurch last week was the fourth international school to be shut down since the new Code of Pastoral Care was introduced in June 2016.

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Christchurch business owner Jo Williamson had a staff member from India who was caught up in the closure, and she was worried about the stress it had put him under.

"You feel for them when they and their families have dished out some pretty serious cash for them to come here." He chose RBMC due to its previous good reputation.

"Obviously he felt assured handing over his money because they were two out of four [deemed 'really good']."

International students felt vulnerable and unsure what the implications were about speaking out, she said. Some were being left in limbo, possibly having two years of study go to waste.

The recent "spate of providers getting into trouble . . . sullies our reputation" among international students.

"Essentially they've been treated pretty badly," Williamson said.

NZQA deputy chief executive Grant Klinkum​ said increased statutory interventions showed New Zealand had a "robust system for ferreting out problems".

"I don't think we should be concerned about our reputation. Those few cowboys that might exist, that's our reason for being."

NZQA monitors about 510 tertiary education providers – including more than 200 international tertiary providers – and last year undertook statutory interventions on 29.

Each provider was given a ranking that identified their quality. There were 245 "excellent" organisations, 208 "really good" organisations, 29 organisations with "some concerns", and one "poor" organisation under statutory watch.

NZQA received and followed up on about 500 "expressions of concern" about providers each year, which could include making surprise visits or taking away student assessments to re-mark.

Last year, 37 applications for new private training establishments were sent to NZQA. Twenty-two were rejected and 15 approved.

Warning signs for a provider included transient management staff, very fast growth in student numbers, and offering low-fee courses.

Fees ranged from $16,000 to $21,000.

Independent Tertiary Education NZ – which represents private training establishments like international schools – agreed recent changes were positive.

"Schools involved in closures were certainly not offering quality. We don't want those sorts of providers," chairwoman Christine Clark said.

Education New Zealand chief executive Grant McPherson said there had been a 34 per cent increase in international student numbers since 2012 – from 98,119 to 131,609.

"Independent research tells us that 90 per cent of international students have a positive or very positive experience in New Zealand. Naturally we want 100 per cent student satisfaction rates, and that’s what we’re aiming for."

Ministry of Education head of graduate achievement, vocations and careers Claire Douglas said international student fee revenue in 2016 was $1.08b, with other contributing revenue totalling $4.5b.

It was New Zealand's fourth largest export industry.

"Ultimately we want all international students to feel welcome, safe and well, enjoy a high quality education and know they’re valued for their contribution to New Zealand."