"It’s exhausting and terrifying," said Dr Mary Bousted.
Education secretary says government will be "putting trust" in teachers after results fiasco last year.
Resits, advance notice of topics and more generous grades are meant to compensate for the interruption to education during the pandemic.
Shadow education secretary Kate Green said Year 11 and 13 students face "a mountain to climb" after losing up to six months of teaching time.
The education secretary was repeatedly asked by interviewers whether he would step down over the A-levels fiasco.
Appeals against grades vary between exam boards, with schools facing charges of up to £150 for each independent review.
Nick Gibb says the government will "apologise to nobody" for the move.
Students will be able to drop subject areas in next year's exams, but teachers fear it could mean even less BAME representation in the curriculum.
Concerns have also been raised that the appeals system could favour the most "well-heeled and sharp-elbowed" families.
For years I’d been told how important these exams were for my future. Now I worry I have no control over the next steps of my life.