The government has published its annual performance data for secondary schools in England to frustration and anger from many teaching unions and school groups. New league table measures have been employed by the Department for Education this year and appear to show that the number of secondary schools below the floor target has doubled between 2013 and 2014.The reason behind the apparent failure is the stripping out of many previously measured qualifications such as some International GCSEs and many vocational qualifications. But the biggest change in the performance data is the inclusion of only the results of a pupil’s first attempt at the exam – retake data has not been allowed in the tables this year.The National Union of Teachers argued that the changes to the league table measures meant that, "yesterday's success story becomes today's failure - even though a school's quality will not have changed".Richard Harman, Chair of the Headmasters' and Headmistresses' Conference and Headmaster of Uppingham School, expressed disappointment at the Education Secretary's controversial decision to strip a selection of unregulated iGCSEs from the tables and then all iGCSEs from 2017."This is an ill advised and illogical decision which creates less choice and more confusion,” said Mr Harman."All Heads want to review their offering solely based on what is best for our pupils.  Many independent schools, like my own, have found the iGCSEs to be appropriate and rigorous, providing a good grounding for sixth form study. They also provide internationally recognised qualifications in an increasingly competitive and globilised world.” "It will be most unfortunate if this decision means performance tables become less transparent and less informative for parents.”Michael O’Sullivan, Chief Executive of Cambridge International Examinations, also commented, “Schools in England have been placed in the curious position where they can choose to prepare students for Cambridge iGCSEs,” he said, ”but will be penalised in the government’s performance tables if they do. You have to ask yourself what their ‘performance’ tables are for – assessing how schools perform, or restricting what they teach?”The change to the performance measure and the decision not to include some of the iGCSEs in the tables has seen top public schools such as Eton College score 0 per cent in the benchmark measure of five good GCSEs including English and maths.Education Secretary Nicky Morgan has responded to the criticism, "For too long pupils were offered courses of no value to them,” said Ms Morgan, “and schools felt pressured to enter young people for exams before they were ready. By stripping out thousands of poor quality qualifications and removing re-sits from tables, some schools have seen changes in their standings.”Teaching Unions have reacted to the changes by creating their own set of performance tables which, they believe, reflects a truer picture of the performance of schools in England, including all iGCSEs and a pupil’s best result in their given subject.