A tricky GCSE maths question stumped thousands of students last week, inspiring them to take to Twitter to vent their anger and frustration.
The equation in Thursday's Edexcel exam was on the probability of taking two orange sweets from a bag. By the afternoon, the topic was trending on Twitter and online petitions were set up calling on the board to lower the grade boundaries when marking.
Edexcel's owner Pearson said it aimed to test the full range of abilities, and that it would ensure students were treated fairly when the papers are marked.
Even though it is understood that the sweets question was targeted at A/A* students, some pupils complained it was of a higher standard than those in past papers used for revision sessions.
One student, writing on the Change.org petition website, raised this point: "All past papers were similar in a way and they are the resources... that were used by students all through the country to help them with this paper... a lot of people have done badly and would appreciate a retake of a new test or lower grade boundaries."
About 500,000 teenagers sat the exam across England, and some took to Twitter to say they felt all was going well until they began the second paper in the maths non-calculator exam.
The question that attracted the most comments was about a girl called Hannah taking sweets from a bag at random, when students were asked to prove the equation: "Show that n²-n-90=0". Other young people highlighted other questions - where they were asked about the cheapest plants at a garden centre, and the volume of two pieces of cheese - as being particularly difficult.
One user said: “The probability of me getting an A* in maths is about as low the chance of getting a dark chocolate caramel.”
Another said: “Pretty sure liquid C was formed of my own tears…”
A Pearson spokesperson told the BBC: "Our exam papers are designed by an experienced team of expert teachers with a deep understanding of the subject matter.
"They make sure our papers are set at the appropriate level to test the full range of students' abilities.
"In the event that any one paper turns out to be more or indeed less challenging than usual, our marking and grading process always ensures students are awarded the grades they deserve."
Ofqual, which regulates exams in England, said it had not been contacted over the Edexcel exam. Even if it were contacted, responsibility would lie with Edexcel to investigate and deal with any issues in the first instance.
It is understood that Edexcel has only received one formal complaint about the paper so far, from a teacher.