The committee's report said it agreed with many of the plans to overhaul GCSEs - such as moving exams to the end of a course and limiting the culture of excessive resits.
But the NUT said candidates who needed several resits to pass the tests were dyslexic, had English as an additional language, or were less familiar with the on-line testing system.
But he added: "This is a really good opportunity for our system and the secretary of state to look at our examination system and ask whether it is rigorous enough, whether it's credible enough, whether what's happened over the last few years in terms of resits, early entries and the modular approach to to examination is actually raising standards".