The ministry previously estimated Otumoetai College's leaky classroom bill to be about $25 million.
"At this stage, the chances are we're going to have to do a major rebuild of this school," Mr Randell said.
"My library roof leaks, my drama-music [department] leaks - there's just different parts of the school that are leaking.
"Anything in our school that was modified prior to 2003 is leaking."
Heavy rain resulted in whole passages being flooded and linoleum being lifted off the floor. The school had already paid about $45,000 in repairs, Mr Randell said.
Other Western Bay schools with leaky buildings include Tahatai Coast School, dubbed New Zealand's leakiest school due to the extent of its classroom woes, Otumoetai Primary, Otumoetai Intermediate, Mount Maunganui College, Tauranga Boys' College, Tauranga Girls' College, Selwyn Ridge School, Te Akau ki Papamoa Primary School and Te Puke High School.
Tahatai Coast School principal Ian Leckie also supported the Ministry's legal action.
"They are looking at ... some kind of redress. [The Ministry] has got every right and part of the responsibility," he said.
His school had undergone multimillion-dollar repairs during the past five years. Some parts of the school could be fixed but most of the school had to be torn down and rebuilt, he said.
Tauranga Boys' College principal Robert Mangan was dealing with problems and work had started on fixing a leaky 14-classroom block
"It's been a significant problem at Tauranga Boys'. We've remediated the science block and gymnasium plus we're working on a nelson block."
Michelle Paddison, associate at law firm Sharp Tudhope, said she was aware of at least one leaky Western Bay school the Ministry was taking legal action over.
The ministry lodged its High Court claim on Wednesday against wall cladding manufacturers, which supplied building materials used in schools affected by weather-tightness failure.
