There has been a wave of anxiety among teachers, following visits from moderators from one of the exam boards, Edexcel. They have found that in almost every case pupils' coursework has been marked down.
Giles Bird, headteacher of Kingsmead comprehensive in Enfield, said: "I haven't seen teachers so worked up for years. Many schools around here are respected for their art and have found their pupils have been marked down.
"Art has historically been a high-achieving subject and there seems to be a real drive to knock down the high levels."
A major concern expressed by teachers is that the moderators are focusing on how well the pupils write about a piece of work rather than their final artwork.
Malcolm Kerr, head of art at Fulham Cross secondary in London, said: "I was quite upset as I marked the coursework according to the criteria and the moderator came in and marked them down because of their written work. We have a high number of pupils who speak English as a second language but he didn't seem to take that into account when looking at their written work."
Head of art at Aylward school in Edmonton, Maria Clemmett, believes this year's pupils have been deliberately put at a disadvantage.
She said: "Edexcel only gave us the new assessment matrix in December when we had been teaching the course for one-and-a-half years. "We had no information up till then on what weight they were putting on certain areas. We are one of the most successful departments in the school and our results are going to plunge."
The Qualifications and Curriculum Authority revised the GCSE art syllabus this year leading to exam boards bringing in more rigid marking criteria.
A QCA spokesperson denied there had been a conscious downgrading of marks by moderators: "The written work for this module of GCSE was optional. Pupils could have used other methods to highlight their objectives such as visual diaries or visual research."
Teachers who have asked for a remoderation have been turned down by Edexcel who said they will have to wait to appeal until after the GCSE results come out in August.
A spokeswoman from Edexcel said: "Following guidance from the QCA on the new criteria, we sent out an assessment matrix to all the schools in August last year. Anyone who is unhappy can appeal after the results are issued."