If you want to work in New Zealand you must apply in advance for a Work Visa. The Work in New Zealand(external link) section of the New Zealand Immigration website contains comprehensive information about the options available including:
Studying in New Zealand
The Ministry of Education(external link) website contains information about the New Zealand education system(external link), and New Zealand’s Code of Practice(external link) for the care of international students.
New Zealand Educated(external link)website provides international students with information and resources including links to institutions and courses(external link) and scholarships(external link) and a guide to living and studying in New Zealand(external link).
Immigration New Zealand has information about how to apply for a student visa(external link).
If the length of the course you are planning to study is designed to last for longer than 3 months, you must apply for a student visa, regardless of how long you plan to study in New Zealand.