Students sang a series of beautiful waiata for Simpson, which was followed by a morning tea with everyone.
A number of former students that Simpson has enrolled over the years now have their own children at Turakina School.
She has seen hundreds of students come and go over the past four decades, including current principal Leigh McKay.
"I remember enrolling Leigh when she was just 5 years old. It was pretty exciting when she was appointed."
McKay said it took around two months in the job to stop calling her Mrs Simpson.
"We won't be forgetting Mrs Simpson anytime soon. Thank you for your care and dedication to the school, you show our school the value of manaaki.
"Thank you very much for everything you have done."
Simpson is stepping into retirement to look after her husband and hopes to spend her extra time working in the garden before travelling around New Zealand during the summer.
"I've seen most of New Zealand. I'm from the South Island so we will go down there I think."