England's General Teaching Council found Maureen Brown, who taught science at Priory school, Southsea, guilty of unacceptable professional conduct.
A disciplinary hearing in Birmingham last week banned the 48-year-old from teaching for a minimum of four years.
Nick Leale, presenting officer, said it was not alleged that Mrs Brown was a dealer in class A drugs. But he told the hearing: "What is clear from the papers and the evidence is that Mrs Brown took possession of high-value heroin and chose to carry this on her person across the city of Portsmouth.
She knew what she was carrying - it was an irresponsible act and unacceptable professional conduct." Mrs Brown claimed the drugs belonged to her sister-in-law, a registered drug-user, who had been staying with her the previous week and she was trying to return the heroin to her.
The disciplinary hearing was told plain-clothed police officers stopped and searched Mrs Brown in August 2002 after following her car from her home to a nearby flat and then on to Southsea.
She admitted having heroin in her possession, and 12 wraps of the drug were discovered in her handbag. Police found 12 more wraps at her home and one in her car boot along with a pestle and mortar containing traces of the drug.
Mrs Brown pleaded not guilty to three criminal charges relating to the possession and supply of Class A drugs in October 2003 and was acquitted at Portsmouth crown court. But she failed to tell the school she had been arrested and was suspended once the police informed it.
Mrs Brown, who did not attend nor was represented at the disciplinary hearing, had taught at Priory school since 1986. She never returned to her job, resigning before the school could hold a meeting about her future.
Brian Shimell, head of Priory school, told the hearing: "The actions constituted gross misconduct - the school considered her position to be untenable. Part of Mrs Brown's professional responsibility involved the delivery of drug education as well as being a role model."
Liz Carter, chair of the disciplinary panel, said: "Teachers are role models for pupils and the panel is mindful of Mrs Brown's responsibility with drugs in this specialist sports college.
"Mrs Brown did not act responsibly to dispose of the pestle and mortar and packages of drugs: rather she took matters into her own hands."