Stephen Watson, formerly head of the technology and information and communciations department at Henbury high in Macclesfield, Cheshire, allowed a Year 11 pupil to copy her classmates' work after he over-marked an incomplete assignment that was going to be moderated.
He asked pupils to present their work for the girl to copy when he realised her incomplete portfolio had to be sent off for examination in January 2003. The school was alerted after a parent complained.
The GTC panel, sitting in Birmingham last Friday, gave Mr Watson a reprimand which will remain on his record for two years.
Ged Ward, headteacher, said: "Mr Watson was placed in a position of trust by the school, the community and the students to conduct the examinations practice both fairly and accurately."
Mr Watson, who was present at the GTC hearing, admits allowing the girl to complete parts of the study after the deadline but denied adapting other pupils' work or allowing the girl to do so, despite confessing to that during a meeting on February 4, 2003.
He resigned after the meeting, which had originally been scheduled to deal with his capability as faculty head.
Mr Watson said: "In January 2003 I was working under considerable pressure and felt totally isolated as head of faculty.
"When I discovered the problem with this portfolio I was under extreme pressure from the headteacher and I thought if there were any problems with my moderation of the portfolios it would have been another thing that he could have checked me on. Under duress, I allowed the student to add the missing pieces of work and sent it to the moderators."
Mr Watson, now working at Hyde technical school in Greater Manchester, said an occupational health report found he was suffering from stress and mild depression at the time and that his concentration and judgment would have been impaired.
But the GTC ruled that Mr Watson had acted in an unacceptable professional manner.