ART assessment has become so prescribed that geniuses like Van Gogh and Picasso would fail their GCSE, art teachers say. Reform of the national curriculum has meant more rigid descriptions of the different levels students can reach in subjects like art and design, music and PE.

The Qualifications and Curriculum Authority changes have led exam boards to introduce “marking straitjackets” say art teachers. And the move to more detailed schemes could mean mediocre students get top grades in GCSE and A-levels, while talented artists are short-changed.

Paul Smith, head of art at JF Kennedy Roman Catholic School, Hemel Hempstead, said: “It is all about proof and documentation rather than the finished product. In fact in most schemes, there is no actual mark for the final piece.”

Students who sat Edexcel art GCSE this year will be judged on both their coursework and exam on six assessment objectives which are worth five points each. They must score marks in each area to pass.

They are expected to record their responses to observation and imagination, use a range of media, analyse work from other times and cultures and make connections between their own work and that of other artists.

Malcolm Kerr, head of art at Fulham Cross School, in south London, doubted whether Picasso would pass. “Are we assessing students as artists or as pupils following a course?” he said. “It is teaching to the test like never before.”

In previous years, teachers who marked work, and whose marking was then assessed by moderators, had more discretion to allocate marks.

A former examiner, and head of art at a school which enters more than 100 pupils for the GCSE each year, said: “The written language has taken on a greater emphasis. Traditionally, there were students who struggled with other subjects but who could excel in art. The move to more rigid marking has severely penalised these students.”

However, Julie Cowdy, head of art at Norton Technology School in Malton, North Yorkshire, said having standardised criteria was the only way to assess pupils’ artwork fairly.

She said: “It’s notoriously difficult to assess art. You either look at a piece of work and you like it or you don’t. The only fair way is by having a standard set of criteria to mark it against.”

Tom Hartney, an art teacher at Vyners School in Uxbridge, said he was initially suspicious of placing more emphasis on pupils’ writing about what they have done. But having gone through the assessment process with a mixed-ability GCSE art group, he said the changes had not concerned him as much as he thought they would.

“The assessment of artwork is contentious, but I think what the pupils are doing now is of a higher standard.”

A spokeswoman for Edexcel said: “The revised matrix is aimed at providing precise and accurate assessment about the pupil’s portfolio. The assessment of a single piece of work has not been in place for a long time.”

Richard Cork, The Times art critic, said: “I would find it worrying if the final piece of work was not taken into account. In the end, that is what it is all about. A work of art is either good or it is not so good. You can fulfill the interim criteria and still come out with a boring piece of work.”