An investigation into her case could force local education authorities to rethink how allegations against teachers are handled.
Welsh Assembly education minister Jane Davidson said she wanted the disciplinary procedures to be reviewed by all LEAs across Wales. She also said she would like to build on guidance from the Department for Education and Skills that LEAs should not automatically suspend staff and called for suspension to be looked at on a case-by-case basis.
Mrs Evans, of St Mary's junior school in Caldicot, south Wales, was suspended for 18 months after being accused of slapping a pupil. In March, she was cleared by the courts of all allegations including bullying, harassment and inappropriate physical handling of her pupils.
A report by the Welsh Assembly has now found she was treated unreasonably by Monmouthshire education authority.
The inquiry found the LEA withheld information from the governing body, including allegations made against Mrs Evans, and that this contributed to a long delay. It also found that the LEA acted unreasonably in failing to give Mrs Evans access to documents until very late in the case.
Mrs Evans said: "We are absolutely delighted with the report. I and the rest of the staff are over the moon. An apology from Monmouthshire council is the least it can do but I can't see it happening. Some LEAs do not have good practice in place and hopefully my case will lead to a national code of practice."
Monmouthshire County Council has welcomed the report. A council spokesman said: "The minister acknowledges that the LEA and the governing body were at all times working in the interests of the pupils at the school and that they were aware of their reponsibilities as employers to ensure the health and safety, welfare and well-being of their staff."
The long delays in Mrs Evans's case led the Welsh Assembly to recommend that LEAs keep any disciplinary procedures to a strict time-scale to be decided beforehand.
Doug McAvoy, general secretary of the National Union of Teachers, said: "As a result, teachers in Wales can feel that much safer against false accusations. I look forward to the lessons of the Marjorie Evans case being learned in England as well as in Wales."
The NUT is pursuing a claim for compensation for Mrs Evans against Monmouthshire council.