Children sitting grammar school entrance exams were given "impossible-to-answer" questions, a parent has said.
The errors appeared in the 11-Plus exam run by the Buckinghamshire Grammar Schools group's 13 schools.
Prospective pupils spotted the mistakes as they sat the exam, a letter from The Gerrards Cross CE School said.
Exam provider GL Assessment and Buckinghamshire Grammar Schools apologised for the errors.
There were errors on two questions on a verbal reasoning paper and two questions on a practice section of an English test.
A mother whose child sat the exam, and did not want to be named, said: "It was impossible to answer and kids began raising their hands - which at the age of 10 under exam conditions takes some courage."
She added it "beggars belief that no-one proof read it".
The Gerrards Cross CE School, a primary school, wrote to parents to say the questions made children "concerned" and "upset" and this may have affected their overall performance.
Read more detail.