Grammar schools in Buckinghamshire have been forced to discount two questions from their 11-plus entry test after it emerged that they could not be answered by pupils.

An email sent to parents by the Buckinghamshire Grammar Schools group, which represents the 13 grammar schools in the selective county, said two questions on the verbal skills paper “could not be answered correctly as the options on the answer sheet did not reflect those in the question paper”.

It also admitted to another “inconsistency” in one of the practice questions in the English section of the same paper.

The group said test centres were instructed to tell all pupils not to attempt to answer the questions.

An investigation into the error on the test is ongoing, and the two questions will not count towards pupils’ marks. The group said it hoped the problem would be addressed “as swiftly as possible”.

The tests have been set by GL Assessment since September last year, with Buckinghamshire County Council providing test administration services.

Every child in Buckinghamshire is automatically entered into the 11 plus test, used to assess which pupils have high enough attainment to attend grammar school, unless they specifically opt out. The tests assess verbal, non-verbal and mathematical skills.

Alexa Collins, a Labour campaigner and member of anti-selective education group Comprehensive Future, broke the news of the error on Twitter.

She told Schools Week: “They said they aren’t going to count those questions but it doesn’t matter. How do you assess the amount of time that has been wasted on them, or the stress it caused?

“The next seven years get decided today for so many. This test has screwed them up.”

Others have also used social media to voice concerns about the test.

A spokesperson for Buckinghamshire County Council said it is seeking an “urgent meeting” with GL Assessment and The Buckinghamshire Grammar Schools Group “to establish a resolution to this issue”.

“We recognise that this will cause anxiety for parents and we hope that this matter can be addressed as swiftly as possible.

“The County Council will be working closely with The Buckinghamshire Grammar Schools and GL Assessment and, as soon as we have a resolution for this issue, it will be communicated directly to parents.”

In a joint statement, the Buckinghamshire Grammar Schools group and GL Assessment said “every effort was made to give instructions to all test centres” to warn pupils not to try and answer the questions.

“An urgent investigation is already under way. However, we would like to assure all parents and candidates that there will be a fair resolution within a very short period of time.

“We sincerely apologise for any anxiety this may have caused the candidates and their parents.”