An A-level student who was given a U-grade in English has got an apology from the exam board after it realised the mark was wrong.
Ms Huddlestone scored 100% in the exam paper
Sarah Huddlestone, 18, from Derby, was predicted to get an A-grade, but was horrified to learn she was given a "U" or unclassified result in one paper.
She feared the result would prevent her from going to her chosen university.
When she challenged the result, the exam board AQA admitted her result was wrong - and she had scored 100%.
Ms Huddlestone, who attended Landau Forte Academy in Derby, has now been given her university place in Lancaster.
"I was pleased that I got the A that I felt I deserved in the first place, but I was disgusted with the exam board - I couldn't believe they had got it so wrong," she said.
"They said I had scored 20 out of 90, which is unclassified, when actually I had top marks."
The initial mark in the English exam paper had lowered her overall English result from A to B - and she needed an A to attend her first choice university.
Her mother Denise Huddlestone said she was afraid other students would not be so fortunate, especially if they had not taken the steps to challenge the result.
The exam board said it was sorry for what happened, but added such mistakes were rare.
It said systems were in place to double check examiners marking, but if in doubt, students should ask their school to challenge the grade.
Exam boards can fast-track the checking of questionable grades to ensure students do get an answer in time to confirm their university place.