But the General Teaching Council for England found Helen Jones guilty of "unacceptable professional conduct, falling short of the standards expected of a registered teacher" and issued a disciplinary order.
Mrs Jones was employed at Walpole Highway primary in Norfolk between September 2000 and April 2001. She was one of two teachers at the 53-pupil school.
Robert Bourns, for the GTCE, said the boys had slipped unnoticed out of a lesson with Mrs Jones and scaled the school gates. They were not missed until a member of the public saw them walking towards playing fields half-a-mile away from the school.
Mrs Jones was also reprimanded for a second allegation, of failing to take reasonable care while a pupil stood on a chair to clean a whiteboard, as another dropped the class goldfish on the floor.
A third allegation of failing to act while a pupil "A" leapt across tables during a lesson was dismissed by the GTCE committee.
During the three-day hearing, Sandra Frusher, the head and only other teacher at Walpole Highway, described scenes in Mrs Jones's classroom as "chaotic", saying, "it was never a totally organised class".
She employed Mrs Jones after they had worked together at nearby Wormegay primary. She said: "I considered her to be a very good teacher, conscientious and hardworking. There was no personal animosity."
Mrs Jones, representing herself, accepted blame for the pupils leaving the school but denied that she had no control over her class and accused Mrs Frusher of telling a "pack of lies" under oath.
The committee heard that pupil "A" suffered from attention deficit hyperactivity disorder, and despite having a learning support assistant was known to be "uncontrollable".
Issuing a reprimand which will remain on the GTC register for two years, Anthony Handley, the disciplinary panel chair, said: "Two boys left your classroom unseen and were missing without you realising.
"We have taken into account your mitigating circumstances - the deficiencies in management at Walpole Highway and the lack of structured support available to you while coping with a child you were not trained to cope with."