Thousands of Muslim pupils in Blackburn, Nelson, Burnley, Rawtenstall, Hyndburn and Preston will be told to boycott all school meals when they return to class in September.
The move follows the decision by Lancashire County Council's ruling cabinet to stop supplying only halal meat from pre-stunned sheep and cattle to 27 schools.
The authority currently provides halal meat from un-stunned animals to these schools attended by 12,000 pupils, three-quarters of them Muslims.
The senior councillors exempted poultry from the requirement for animals to be stunned before slaughter.
County leader Cllr Geoff Driver, who championed the move, said: "This decision has been taken solely on the grounds of animal welfare."