DUP MP Ian Paisley has dismissed the expert evidence of a highly-esteemed educationalist who accused some schools of being "exams factories".
The Northern Ireland Affairs Committee at Westminster is holding an inquiry into education funding in Northern Ireland.
It heard from Sir Bob Salisbury, a former school principal who previously led an independent review of school funding.
Also selected to chair a literacy and numeracy taskforce, Sir Bob has an international reputation for his thought-provoking ideas on leadership styles and staff motivation.
Sir Bob told the committee of MPs that it was an "enduring myth" that Northern Ireland had one of the best education systems in Europe.
"It has a long tail of underachievement and that long tail of underachievement is still there and it's stubbornly there, and it's not really being tackled," he said.
"The school system - the success of it - should be measured on how it treats the least able youngsters in its society, not how it treats the most able.
"Some of the top schools in Northern Ireland for the top students do extremely - well, often they're exam factories which creates the stress but they do very well."
He added that many children were not getting the qualifications and the start in life that they deserved.
"We can bury our heads in the sand and try to convince ourselves that the problem doesn't exist, or we can try to do something about it," he said.
Mr Paisley, however, said he felt such comments were "talking my country down".
"I've only been in the room 20 minutes, but I must say I feel you've talked Northern Ireland right into the gutter," he said.
"Congratulations, if I was a child listening to this I'd be depressed listening to you two."