Claims senior school students in the Auckland region will be severely affected by the Covid-19 Alert Level Three lockdown.

For the next 11 days, Auckland students in years 11 to 13 cannot attend school, and will have to learn from home.

Other students are being told to stay home, but if they can't be supervised, they can go to school.

Auckland Grammar headmaster Tim O'Connor told Francesca Rudkin it's an unfair disadvantage for students who are preparing for NCEA or Cambridge exams.

"The loss of face-to-face teaching, you can't underestimate the impact of that, it will be significant. So there will be two weeks loss compared to the rest of the country."

He says it makes "absolutely no sense" to him why they aren't allowed to return.

"When we can put in place appropriate health and safety measures to get students back into class, to be physically distanced, and get on with some form of learning."