Final-year students plan to sing the school song at Mt Albert Grammar School today after they were shut out of the school on their last day of regular classes.
About 130 of the school's 450 Year 13 students have signed up to a Facebook event planned after headmaster Pat Drumm called a special assembly yesterday to tell the students not to go to school today.
He said he wanted to let teachers attend today's Year 11 prizegiving, but also avoid "silly stuff" that has happened in past years on the last day of school, such as water fights and boys and girls swapping uniforms.
"Yes, it's also to send a pretty strong message that it's business as usual, and while it's a special day for the Year 11s, we don't need any of this silly stuff that can creep in at this time of the year," he said.
Year 13 student Ryan Naran said students were "outraged" by the last-minute decision, which meant they were unable to say goodbye to each other and to their teachers.
Another student, Tom Barrand, said the students planned to enter the school as a group at lunchtime, defying Drumm's order.
"It's more of a sit-in than a protest," he said.
"It's a mature way of getting to say goodbye to everyone, so we can have that last day and hopefully prove the senior leadership team wrong that we can have a really positive afternoon."
A screenshot from the private Facebook event page says: "Most of yall mad as hell that you aint got the last day, so we gonna meet at Rocket Park, walk up to MAGS, do some kind of sit in, chill, show the school that they made a mistake not trusting us."
Tom Barrand said students would be wearing school uniform.
"We'll go and sit in the school quad and sing the school song," he said.
"Someone will go and give the teachers the presents that we have bought for them. We will have a chance to say goodbye."
If they are not allowed in, he said, "We'll just stand out in front and sing the school song, and hopefully we can see our teachers for the last time. That will be really nice because they have had a really big impact on all of us over our five years in the school."
Drumm said the students would have a chance to say goodbye to their teachers on Monday at the Year 13 prizegiving.
But Tom Barrand said not all students would attend the prizegiving and Monday would only be a half-day so there would not be time to see all their teachers.
"We have kind of had the rug pulled out from under us," he said. "Hopefully we can maturely and politely express our disagreement with the course of action our leadership has decided to take."