This follows an embarrassing defeat suffered by the council's educational leadership on Tuesday over its lengthy efforts to rename the 125-year-old Nicolson Institute in Stornoway.
The full council decided by 18 votes to eight to retain the Nicolson name when it is amalgamated with Lews Castle School, the town's other secondary. This reverses the narrow 10-9 decision of the education committee to hold a pound;5,000 referendum on the issue.
The Rev Tom Sinclair, who chairs the Lews Castle school board, said it would now consider whether to seek a judicial review and referral to the local government ombudsman.
A petition signed by 7,700 islanders called for the Nicolson name to be retained. But Donald Mackay, vice-chairman of the education committee, said last month that assurances had been given at public meetings on the merger that the name would be settled by a referendum.
Mr Mackay's warning that a U-turn would create a sense of betrayal was ignored by the full council. Many felt that the controversy had gone on long enough. As one councillor put it, they should take an immediate decision without a referendum as a form of "damage limitation".
The action group backing the Nicolson name said it looked forward to "a period of educational calmness and consolidation".