The student they care for will need to apply for a variation of conditions
For students in school years 1 to 8, and younger than 13, living with their guardian is a condition of their student visa. The student must apply for a variation of conditions.
The education provider must arrange for alternative care during the guardian’s absence.
The guardian may remain out of the country for no more than 4 weeks
Details:
https://www.immigration.govt.nz/new-zealand-visas/already-have-a-visa/my-situation-has-changed/visit/i2019m-on-a-guardian-visitor-visa-and-need-to-travel-home-for-an-emergency
简单的说，在新西兰读1-8年级，年龄小于13岁的国际生，与监护人住在一起是学生签证的条件之一，如果监护人临时要回国，学生必须申请签证条件的变更。学校必须安排临时照顾人接替监护人照顾学生，同时监护人离开新西兰的时间不能超过4周。
详细规定请见以下链接：
https://www.immigration.govt.nz/new-zealand-visas/already-have-a-visa/my-situation-has-changed/visit/i2019m-on-a-guardian-visitor-visa-and-need-to-travel-home-for-an-emergency
