Wanganui City College principal Peter Kaua said students most commonly changed schools because their family was moving out of the area.
He said three families from out of town had recently arrived in Whanganui then returned home after a short time.
That happened when a family couldn't find work or housing.
"Work is the big one," said Mr Kaua.
Changing schools often wasn't good for learning, adjusting to the school spirit, and getting used to teachers, he said.
"Most of them are good kids. I just feel sorry for them having to move for one reason or the other."
Mr Kaua said the school didn't have too many transient students and it tried hard to keep students at school.
"The ones that I do get that come from out of the area usually come because the housing is good here and they stay," he said.
According to the Ministry nearly 3800 students were recognised as transient last year nationally.
Of those, 87 per cent transferred school twice, 11 per cent three times and 2 per cent four or more times.
Maori students were the ethnic group with the highest levels of transience.
There had been consistently higher rates of female transient students.
The rate of transient students was generally higher at younger ages, apart from a spike in the rate of transient students at 14 years of age. That was one year after the transition into secondary school and before beginning NCEA.
Generally the number of transient students decreased as decile increased, according to the Ministry.
Students who had moved school twice or more across Year 9 to 11 were less than half as likely to achieve NCEA Level 2 or above by the time they left school compared to those who had not moved school.