No matter how hard you worked today, your inputs are up and your outputs are down. If schools were widget factories, production would be shifted to China.

Number crunchers at the Office for National Statistics looked at how much money was poured into education, compared with factors such as GCSE results and attendance levels, and came up with this devastating assessment.

Using a complicated formula to “measure the unmeasurable”, they revealed that despite a near doubling in education spending from pound;27.2 billion in 1996 to pound;49.4 billion last year productivity had changed little overall since 1996.

And the reasons? Well, it was those workload reforms, which introduced 50,000 support staff into the classrooms. Of course, the researchers were unable to say just how much unpaid overtime teachers were doing before then. Falling pupil numbers were also blamed.

Joe Grice, executive director for social and public services for the statistics office, said overall there had actually been a slight increase in productivity over the past 10 years because of a sudden increase between 1996 and 1999. “We would be hoping to get more,” he admitted.

John Dunford, general secretary of the Association of School and College Leaders, said he defied anybody to produce a formula with simple input and output measures for education.

Jim Knight, schools minister, who recently called on schools to make efficiency savings, spoke up for teachers, pointing out that the calculations did not take into account how schools were helping to improve children’s life chances.