Hundreds of papers are being reviewed by an exam board after a marker forged her way to become a teacher by faking degrees on her home computer.
Julia Rawlinson, who claimed to be a science teacher, deceived schools for four years, during which she marked A-level exams.
Edexcel admitted it had no way of determining how many papers had been marked by Rawlinson as examiners grade individual questions rather than an individual marking a whole paper.
After lying to gain employment with exam board Edexcel, she was then offered a post teaching biology at a Devon school.
Westlands School, Torquay, became suspicious after photocopied degree and doctorate certificates appeared to be fakes. The fraud came to light when the school ran a criminal records check and contacted the universities which she claimed had awarded her the certificates.
The school's head Dr Colin Kirkman said in a statement: "Julia was an examiner for A level Biology with the Edexcel exam board. The exam board offered us her help and support prior to the summer with A level Biology project work, which we accepted.
"We understand she also worked in at least two other schools in this area in this capacity.
"However, we noticed that her exam certificates were photocopies. Torbay children's services commended us for the extensive checks that we made — the depth of the checks that exam boards and other organisations failed to make."
Rawlinson, from Brixham, forged degrees from a South African university and Glasgow Caledonian University, as well as a fake qualified teacher certificate from the General Teaching Council for England.
She admitted she had made them up using graphics from the internet and had never completed a degree.
The 44-year-old appeared in Torbay Magistrates' Court on two charges of fraud by false representation and three counts of making a false instrument under the forgery and counterfeit act, This Is Devon reported.
An Edexcel spokesperson said the company was "appalled" by the incident.
“We can confirm that a marker was contracted for marking services by Edexcel for various examinations over the past four years.
"Based on information we have now received, she will not be contracted again in future."
But the board sought to reassure the public, adding: "Markers do not play any role in setting questions."
Steph Warren, head of Edexcel GCSE geography was caught boasting how "easy" her exams were for students. The Edexcel official , who is responsible for setting exams for tens of thousands of students, was captured on film saying: "There's so little content we don't know how we got it through."
Rawlinson was committed to Exeter Crown Court for sentence on February 20.
The school which helped expose Rawlinson