Radio Kiribati reported late Wednesday that a council survey of Nonouti island, where the ferry departed on January 18, showed there were 88 people aboard.
It said they included 10 children of primary age and 13 high school students.
The youngsters are believed to have been travelling to the Kiribati capital South Tarawa for the start of a new school term.
Only seven people, including a 14-year-old girl, have been found alive so far and hopes are fading of locating any more.
Four aircraft, from the United States, Australia and New Zealand, are combing vast swathes of ocean looking for survivors, along with six boats.
Kiribati President Taneti Maamau told public radio Wednesday that the sinking was a "tragic moment" for the tiny island nation but the search for survivors would continue.
"There are objects that have been spotted like wooden pieces and a gas cylinder and a few other things, but sadly there are still no signs of people spotted yet," he said.
Former president Anote Tong said Nonouti had lost its "youngest and brightest" and the whole of Kiribati was in shock.
"This is by far the biggest disaster in terms of numbers and also in terms of the people involved," he told the Australian Broadcasting Corporation.
Tong said there were questions about why it took authorities more than a week to raise the alarm after the ferry, MV Butiraoi, set off on a passage that was only supposed to last two days.
The seven survivors were found drifting in a dinghy on Sunday and the search is now concentrating on finding a life raft that was launched from the sinking ferry.
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