When this said student, I figured it was an 8 year old. Not a PhD candidate. While technically accurate it does tend to sensationalize it a bit.
Not sure if that applies elsewhere in the world, or even if it's still a thing in New Zealand.
Definition: a person who is taught by another, especially a schoolchild or student in relation to a teacher.
It's just that in primary school you have a single teacher all year so the teacher refers to you as their pupil.
While in high school you have many teachers so you're one of their students.
But it's often interchanged.