Schools are rigging results by pointing out the right answers to pupils during Sats, and teachers have been forced to complete their students' GCSE coursework "under duress", it has been claimed.
According to delegates at the National Education Union (ATL) conference, some teachers have inflated grades after coming under "pressure from senior leadership".
Bob Groome, from the union's Norfolk branch, said he frequently supported members facing a capability process "due to the fact that [their] classes are not making sufficient progress according to the data held".
However, he said that digging into the school's overall records often revealed "a problem with the data”.
"I’m quite often quite astounded at how the grades have been inflated in comparison to the original data," he said. "Quite often this is done by heads of department under pressure from senior leadership."
"We’ve had other instances where schools hired in extra support for pupils during Sats examinations, in order to enhance the pass rate. In other words, they’re sitting next to the child and they're pointing at the answers."
Mr Groome said that at one school in which this was happening, a teacher blew the whistle, which resulted in the headteacher being removed. However, he said the academy trust – which he did not name – was "able to cover up the issue".
He added: “There have been other incidences of staff completing coursework for pupils under duress in order to enhance GCSE results. This is totally immoral."
Another union delegate recalled how a teacher had falsified data to show that a pupil who barely attended classes was making strong progress.
“I’m aware of a pupil who attends less than 40 per cent of his lessons," he said. "He’s in school, he just doesn’t engage with them and chooses to sit out of the lessons. When he is in the room, he ignores the work. He had made no progress since September.
"He had flat lines across the board. Except in the lessons taught by the head of teaching and learning of that school, where that boy had made five sub-levels of progress since September.
"Further examination into this teacher…has revealed almost equal amounts of progress for all of his pupils."
The delegate said the teacher in question was "going through a capability soon".
He added: "Data is very easily manipulated and, yes, the benefits of fraudulent data are tempting.”
The conference passed a motion instructing the union's executive to "carry out research into the extent to which the falsification of data is being used to wildly inflate grades, and the impact this is having on target-setting, league tables and performance-related pay".