SNP councillors Keith Small and Ian Mackay said the scope of the consultation on the future of the schools estate is too small and only gives participants the chance to comment on a limited number of options.
They claim the council should have allowed more time for initial consultation before agreeing the questionnaire, which will be sent out to 10,000 households. Mr Small said the SNP only agreed to a review on the basis that any consultation would be "open, transparent and inclusive".
He added: "The consultation so far fails these three tests. We did not agree to a process that prevents people from making their views known.
"This decision will alienate parents who will feel they are not being heard and the council have already made up their mind about certain schools."
Council leader Rhondda Geekie said questionnaires will include a space for alternative suggestions.