Prime Minister David Cameron has warned of a \"hidden crisis\" of \"coasting schools\" in well-off areas that fail to push pupils to their full potential. Writing in the Daily Telegraph, he said schools where \"a failure to reach potential\" is masked by a \"decent local reputation\" would be held to account. He highlighted plans in England to publish progress measures for low, medium and high-attaining pupils. This would \"shine a light on secret failure\", he said. Mr Cameron pledged to tackle the issue of coasting schools in September and in his party conference speech. He now sets out how the government intends to do this. Data that will show whether schools are performing as well as they should be for all their pupils is to be included in forthcoming school performance tables. \"Spotting the real problem schools, looking at the league tables and sending in the inspectors to sort them out is relatively easy,\" Mr Cameron said. \"But it is just as important to tackle those, all over the country, content to muddle through - places where respectable results and a decent local reputation mask a failure to meet potential. \"Children who did well in primary school but who lose momentum. Early promise fades. \"This is the hidden crisis in our schools - in prosperous shires and market towns just as much as the inner cities. \"It is vital to shine a spotlight on secret failure by giving people the information they need,\" he wrote. \'Bs into As\' The problem posed a challenge, he said, \"for all parts of the country - places where governors, parents and teachers might never guess things might be wrong\". \"Why should we put up with a school content to let a child sit at the back of the class, swapping Facebook updates? \"Or one where pupils and staff count down the hours to the end of term without ever asking why B grades can\'t be turned into As?\" Under the changes to the school league tables, data on the proportion of children making average progress between the end of primary school and GCSEs will be published. This will be broken down into low, middle and high attaining groups. The Department for Education said the data would identify schools which overly focus on getting GCSEs for borderline pupils.