Johanna said she had been speaking in assemblies trying to get other students to come on board. About 40 had signed up in the end.
Students would be building their own shelters using tarpaulin and bamboo, they would decamp to the the former sleeping quarters of the schools' nuns in case of emergency.
"It's gonna be cold. We're allowed a small foam roll and thermals and jumpers and stuff," Johanna said ahead of last night's effort.
Guidance counsellor for the Whangarei school Damian Pullen said the activities throughout the week were designed "to give students experiences which help them to appreciate their privileges and how people live in other countries".
Year 12 Joiemaia Lubrica said she had opted to live on $2.50 a day all week.
"You can apply it to how about 3 billion people in the world actually live," she said.
"Today I've had half an apple and really runny curry ... and a lot of water."