Curriculum changes 'rushed' and could create chaos' 12 April 2013 Last updated at 14:24 Controversial plans to change what has to be taught in England's schools are being rushed in and could "create chaos," head teachers say. The Association of School and College leaders say the national curriculum changes "cannot be implemented" by 2014 as the government desires. It also warns that some parts are so difficult they could create more disaffection and failure. The government does not intend to delay the plans. ASCL, which represents many secondary heads, has called for an extension to the consultation which ends next week. Drop in standards It says the vast majority of secondary schools are happy with the current curriculum, Its general secretary Brian Lightman said: "The scope of this consultation is vast, covering all subjects and all year groups, and the overall approach and the philosophy behind it are very different to what many teachers have worked with in their careers. Teachers need more time to digest it, to understand the implications and respond fully to the proposals. He added: "Teachers and school leaders feel that they have had no ownership of this new curriculum. Teachers are not resistant to change but they have valid, well-justified concerns about the programmes of study in some of the subjects. If their views are not taken on board, there is a real danger that implementation will be rushed, poorly implemented and could result in a drop in standards. There are also concerns about the nature of the reforms, with Mr Lightman saying that in some subjects the "level of challenge is extremely high" while in others it is "vague and unhelpful." "There is a difference between challenge and making learning more difficult, which could potentially lead to more disaffection and failure," he added. Mr Lightman added that the education secretary would have to "rely on school leaders" to lead the implementation of whatever revised national curriculum was adopted. "So," he said, "it would be an own goal to plough ahead without engaging school leaders more widely in its final development." The head of the National Association of Head Teachers, Russell Hobby, echoed these concerns, saying the government had failed to sell the reforms to the teaching profession. If teachers don't believe in the curriculum it won't work. Because once the classroom door shuts, it is what inspires teachers that gets done," he said. He added that there was still anxiety about how the Department for Education was going to respond to the wide-ranging concerns raised by many of the academics, teachers' leaders and others who had been involved in the formulation of the plans in the run up to their publication. He said many of those who had been asked what should be included were quite shocked to see the nature of what was published in the end. Ambitious The new history curriculum has been dubbed "unteachable" while the maths curriculum is said to be too challenging, with children being asked to cover some areas as many as two years earlier than at present. Some English teachers are critical of what they say is a prescriptive focus on spelling lists and grammar that does not relate to children's use of language. The Department for Education said its draft national curriculum was challenging and ambitious. It added: "We put out a call for evidence over two years ago and we received over 5,000 responses so far from teachers, academics and experts. We are now consulting widely on our draft curriculum. Extending the consultation period would delay implementation. A whole year of pupils would miss out on a more rigorous, knowledge-focused curriculum.