Wales' main exam board has apologised after A-level papers were given out missing vital parts of their questions.
The WJEC insisted the blunder in Tuesday's English language and literature paper was "a rare occurrence" and was being taken seriously.
It insisted robust procedures would ensure students were not disadvantaged and would get fair grades.
But a headteachers' association said it was "astounded" by the mistake.
Schools and colleges contacted the exam board after four pages were missing from the exam.
Excerpts from three Shakespeare plays - Much Ado About Nothing, Othello and The Tempest - were either partly or fully missing.
