Via a letter to parents and anonline statement on Thursday afternoon, Whanganui High School revealed there had been a confirmed case at the school this week.
The health and wellbeing of the children, staff and community was "a top priority," the statement said.
"The student was at school earlier this week for one full school day and a very short period of another day."
"If your whanau hasn't been vaccinated, please do so as soon as possible. You can book on-line at bookmyvaccine.nz or by calling 0800 28 29 26. It's free."