Grammar school pupils progress faster and outperform children of similar ability who attend non-selective schools, official data has disclosed for the first time.

In a major boost for Theresa May's plans for a new generation of selective schools, an official analysis of GCSE results has found that children benefit from grammars.

The data also found that children who were previously not high attainers make even more progress in grammar schools than their highly performing peers.

Justine Greening, the Education Secretary, said that the figures give the Government “even more reason to make more of these good school places available in more areas”.

Ministers will use the analysis to justify Mrs May’s focus on grammar schools, which has been heavily criticised by the Labour Party and some campaigners.