Pamela Ward (above), who was head of Kilnhurst primary in Mexborough, South Yorkshire, claimed stress over staff cuts led her to alter 14 key stage 2 maths papers in May 2005 by mistake.
However, a hearing by England's General Teaching Council in Birmingham found her guilty of unnacceptable professional conduct.
The committee heard that Mrs Ward, who has taught for 30 years, received a positive inspection report in 2002, a year after she became Kilnhurst's head. But she came under pressure in 2004 when a pound;100,000 cut in the school's budget meant she faced making six staff redundant.
Mrs Ward claimed a series of events on the morning of the national tests broke her routine and left her stressed. She said she was not sure what had happened, but that she may have marked the exam papers mistakenly thinking they were optional test scripts.
Victoria Windle, her representative, said: "There was an argument with a member of staff over redundancies which led her to sobbing throughout the day. Mrs Ward didn't know what she was doing."
An external marker spotted changes to pupils' work in another handwriting, leading to an investigation and Mrs Ward's resignation.
Angela Stones, the committee chair, said the panel had looked at the papers closely. "They appear to demonstrate a systematic approach to amending the pupils' work with the intention of benefiting the pupils at the school,"