Tens of thousands more 16-year-olds than last year will need to resit their English and maths GCSE exams.
More than 167,000 students in England received grade 3 or lower on their maths paper, about 21,000 more than in 2022, while 38,000 more, 172,000, failed English language - the highest number in a decade.
Headteachers' unions have said this will put more pressure on colleges.
It comes as the overall number of GCSE passes have fallen for a second year.
One parent, who wishes to remain anonymous, has told BBC News her son performed really well in English, music, art, media and photography, achieving As and Bs, but is devastated as he failed his maths exam despite working incredibly hard and receiving extra tutoring.
Her son, who is autistic and has dyslexia, is a talented musician and film-maker and had planned to take A-levels in film studies and photography and a BTec in music production - but one of these will clash with his maths-resit classes, so he is now having to take different subjects.
"All he can see is the fail - it's torture," she said. "And now he has to spend hours working on a subject he doesn't like and is rubbish at."
