The National Association of Schoolmasters/Union of Women Teachers is balloting staff at Manton Junior School, Worksop, after the boy arrived at school wielding a baseball bat.
The headteacher twice excluded the boy from school, but both times the governors agreed to his reinstatement. The union says his first exclusion, in June, came at the end of a year's disruptive behaviour, including threats and violence to teachers and fellow pupils.
Before the date he was due to return, he turned up at the school gates during break swinging a baseball bat.
On 17 July, he was again excluded for violent and disruptive behaviour but the governors agreed to reinstate him after an appeal from his parents.
The NAS/UWT has recently threatened to strike in two similar cases, in Nottingham and in Hebburn, South Tyneside.
The Government is reviewing the system of appeals against exclusions, in which parents can ask first governors and then an independent panel to overturn headteachers' decisions.
Nigel de Gruchy, general secretary of the NASUWT, said: "If strike action is the only way good order and safety can be maintained, then so be it. However, if so, it must be an appalling indictment of today's society."Reuse content