Banding in schools is will remain in place, according the the Education Minister Leighton Andrews.
He was responding to a question asked by Plaid Cymru member Llŷr Huws Gruffydd during education questions on 6 March.
Mr Gruffydd wanted to know whether Mr Andrews would reconsider the status of the banding system if it transpired that banding was having a negative effect on the number of pupils in schools in the lower bands.
"Banding was a manifesto commitment; banding is working; banding is driving up standards; banding will stay," was Mr Andrews's unequivocal reply.
Plaid Cymru's leader Leanne Wood asked Mr Andrews if he thought that the fact that Llanrumney High School, which has been earmarked for closure, had "climbed more than twenty places in the latest banding table" showed that the banding system had been "undermined".
Mr Andrews replied that Ms Wood "did not understand the banding system", and that "most schools stayed in the same band or moved up or down one place".
"I wish for once I heard something from Plaid Cymru that showed they have an interest in education," added Mr Andrews.
Acting Conservative spokesperson Nick Ramsay asked whether Mr Andrews could "offer assurances that the action you took was not taken to crudely lower boundaries to try and cut an attainment gap legacy."
His question related to the announcement that Welsh GCSE grade boundaries will be set in Wales in future.
The minister gave his assurances, and further encouraged members "not to talk down Welsh qualifications".