Members of the National Association of Schoolmasters Union of Women Teachers at Bristnall High School in Oldbury, West Midlands, voted this week not to teach the Year 11 boy. The National Union of Teachers has said it may also ballot its members.
The teacher needed hospital treatment. Although there was no permanent eye damage, he has been off work since just before Christmas. A spokesman for Sandwell education authority said: "He has recovered physically but is still unable to return to school. He is suffering from trauma."
Bob Dyson, the head, and his governing body expelled the boy, who has already been temporarily excluded, after the incident, and their decision was ratified by Sandwell Council. But when the pupils' parents took the case to the statutory appeals panel, the school was told to take the boy back.
Since the panel's decision, the head has made arrangements for him to be supervised in isolation.
Tarsem King, council leader, said: "We are aware of the ballot result and we have held initial discussions with them and while accepting they refuse to teach the pupil, the authority and the school have a responsibility towards the pupils and all others at the school, and will be making appropriate arrangements. The alternative would mean we were not meeting our legal obligation to the pupil and all other children in the school."
A spokesman said negotiations with the parents and the school would continue. Union leaders said the appeals panel had ignored recent legislation which says the effect on all the pupils and the staff in the school should be considered.
Nigel de Gruchy, general secretary of the NASUWT, said: "I congratulate members on taking a firm and courageous stand."