The Department for Education's latest figures on phonics test and key stage 1 assessments show that disadvantaged pupils are trailing behind other children by up to 18 points. The expansion of grammar schools would only entrench that divide.

Commenting on the figures, Nigel Fletcher, Bright Blue's Head of Research, said:

"It’s encouraging that overall attainment in the phonics tests has risen, and that free schools are performing particularly well. But the new Key Stage 1 assessments show some worrying discrepancies in outcomes, with disadvantaged pupils trailing behind other children by up to 18 points. This attainment gap is considerably wider than under the old test standard.

"This presents a significant challenge, given the renewed debate around academic selection at age 11. The least advantaged pupils are falling behind long before that point, and an expansion of grammar schools would simply entrench that divide.

"The evidence continues to show that earlier intervention is where efforts to promote social mobility are most effective, and that free schools and academies are able to achieve excellent results without a selective intake."