Nigel Turner, 57, who taught at Forncett St Peter primary, in Norwich, admitted misconduct.
The council's disciplinary panel, sitting in Birmingham this week, heard that the failure to report the incident meant that the pupil had been sent back into a potentially violent home. It ruled that Mr Turner cannot be named as a child protection officer (CPO) at any school and must tell future employers about the GTC sanction.
The pupil had arrived at the school on October 4, 2004, with bruising around the eye and cheek. A teacher noticed and reported the incident to Mr Turner. Despite repeated reminders from staff, a trainee teacher eventually reported the case to social services a day later.
Mr Turner, who had been a headteacher and CPO at another school before joining the special needs school in 2002, said that he had been "disappointed and bewildered" that staff had gone over his head.
But he admitted: "I forgot. It's as simple as that. It was not acceptable.
I had been working hard through lunch and afternoon break and had intended to deal with the matter."
Julia Corney, the trainee teacher, had asked Kathie Steel, a classroom assistant, to speak to the child. She said: "Myself and two teaching assistants noticed that the pupil had a mark over the eye and cheek. We asked the pupil what had happened and got a vague response. I asked Mrs Steel to speak to the pupil and she was told that the pupil had been smacked by the father and locked in a room.
"Mr Turner offered no advice. I expected him to say 'I will phone social services'. I expected him to tell me what was going on, that he would come to the class and look at the pupil's face."
Ian Cooper, senior personnel consultant at Norwich county council, said that social services should have been told there were concerns about a child's welfare.
"In this incident, we determined immediate action to be before the end of the day as the child was returning to a potentially violent home. Mr Turner's defence had not been reasonable."
Mr Turner said he believed that the matter had been dealt with by other members of staff on the same day. He blamed exhaustion and stress on his failure to act.
He said: "I had been over-worked at the time. The headteacher was away with illness and I had taken on a lot more work. Aside from this, my wife had been ill at the time and my parents had died. I had also just got over testicular cancer."
Mr Turner resigned from his post in January 2005 and is now working for the Forestry Commission in Norfolk.