"Their condition has improved."
One student was transferred from Auckland Hospital to North Shore Hospital yesterday, a Waitemata District Health Board spokesman said.
"The patient is still stable and we're expecting to release them pretty soon."
The fifth pupil was treated at the scene but did not need to go to hospital.
A police spokeswoman said no charges had been laid as of yet, "but the investigation is ongoing".
In an email to parents, the school's principal, Jane Stanley, said counselling support was on offer for all students and staff.
"Our thoughts are with the students and families involved in the terrible accident."