Whangarei Girls' High School principal Anne Cooper said attendance had been steadily improving at the school over the last few years but unfortunately had dipped this year.
She said a few students with very poor attendance could skew overall attendance - especially when the school was unable to make contact with family, and students remained on the school's roll until they had been absent for 21 days.
Ms Cooper said text messages were sent home on a daily basis to families of all students not in their first class of the day. Parents were able to check attendance through the parent portal.
Teachers and deans followed up on absences with students and whanau.
"This includes home visits by a team including some or all of a guidance counsellor, deputy principal and house dean. Each case is treated on an individual basis and a range of interventions can be put in place, depending on the reason for the absences," said Ms Cooper.
Referrals for students under 16 years of age were made to Attendance Services.
Most absences at the school were explained and the most common reason for absence was illness. This year had been particularly bad with a flu many people took a long time to recover from, she said.
Ms Cooper said parents would sometimes take their daughters on holiday during term time for a variety of reasons.
"Our staff are under no obligation to provide for students in this situation but most do when it is requested. However, it does add to teachers' already considerable workloads to provide work."
The national absence rate increased slightly last year on the previous one. The proportion of justified absences remained unchanged, so the increase in the national rate was due to more unjustified absences, according to the ministry publication. The total unjustified absence rate was 4.6 per cent compared to 3.9 per cent in 2013.