Carol Holland Day, who was a humanities teacher at Acton High School in London until Easter 1993, was told by the tribunal chairman that she had "ploughed her own furrow".
At an earlier hearing in March, the tribunal heard that Ms Holland Day had alleged a campaign against her by other members of staff. One former colleague, Chris Burke, said "a definite attempt was made to make life as unpleasant as possible for her".
But Ms Holland Day was the subject of a disciplinary hearing in June 1992 following allegations of abusive language against colleagues. She was given a written warning. The tribunal found that a second disciplinary hearing initiated by the headteacher, John Leavold, was justified following further incidents of verbal abuse.
Mr Leavold said after the proceedings: "We always felt we were very fair and never thought for a minute we would lose. But I felt sad for the teachers involved in this matter, who in my view have always acted very professionally.
"However, justice has been done and we can now get on with the job of offering an excellent education for our students."